Steven was born as the first natural Human/Gem Hybrid, his father being a human named Greg Universe, and his mother being the Crystal Gems leader herself Rose Quartz. He grew up in Greg's care mostly, but once he got older he began to go into the Crystal Gems and start to learn their ways, and become apart of the team himself. It was during this that his first mission, which was going to the Lunar Sea Spire occurred as a sort of test by the Gems themselves, which he apparently didn't do so well in.
When Amethyst got her gemstone cracked, Steven, along with Pearl and Garnet, took her over to Rose Fountain, only to find that the place was covered in Plunder Vines. Unaware of his healing powers at the time (at least how to use them), Steven tried his best to use them in the same manner as his mother, ala tears, though many of these attempts didn't work. He brought Amethyst to the fountain itself, and was told to wait with her as Pearl and Garnet fixed the fountain up. It was during this that he was attacked by the vines, only to be rescued by Twilight Sparkle, moments before the fountain activated again. He immediately explains to the other Gems of Twilight's involvement, and was agreed to let them stay until they could find their way home. The next morning, Garnet tells Steven to give them a grand tour of Beach City, which involved showing them to his dad, along with the other areas of town. After the tour, he runs into Discord, and was given his Portal Key by him.
Sometime later, he begins to learn about the concepts of school from his friend, Connie Maheswaran, and tries to replicate it at home when Pearl presents him with Lapis's Mirror. Steven took an interest in it, and decides to take it out with him, where he and the mirror have some fun together as "Beach Summer Fun Buddies". When he tries to present it to the others though, they try to take it away from him, to which Steven promptly flees. He manages to isolate himself and says he wanted to help Lapis, eventually leading up to Lapis Lazuli's release. Before the Crystal Gems could reach them, Steven's Portal Key opens a portal to Equus, Steven and Lapis falling in. He and Lapis end up in the Castle of the Two Sisters, reuniting with the Mane Six once again, and introducing them to Lapis Lazuli. Steven then reveals about his healing powers, discovering them to be from his spit rather than his tears, and he uses that to heal Lapis's cracked gemstone. Having no method to return home, he and Lapis stayed in Ponyville, in which they got involved in the A.K. Yearling trouble. It took a few days before Steven was eventually reached, and he and Lapis decided to give Pearl and Amethyst a tour of Ponyville.
From there, Steven mainly spent it as aid to the other Gems and the Ponies of Ponyville, going back and forth between Earth and Equestria, which included helping the Gems when they got affected by Poison Joke, and helping the injured players during the tryouts for the Equestria Games with his healing powers.
During one trip back home, Steven took sight of something outside in the Warp Space, using one of the Warp Pads. Worried, he got the others to look around the other Gem locations to figure out what it was, getting more irritated and troubled the less they find, to the point when he begins to argue with Pearl directly. He only calmed down when Rainbow Dash and Fluttershy agree to watch over the Galaxy Warp for him just to be sure. This eases his nerves, and after a day or two calms down completely. During one chat with Lapis he manages to convince her to take him to the Prime Kindergarten to see where Gems grew up, much to Pearl's dismay and worry.
After sometime however, Steven ends up having a dream and first meets Sombra, who tells him that the other Gems don't care for him and only want Rose Quartz. Steven was convinced that there was some way, and followed Sombra's instructions to a remote location, only to find out that it was all a lie and a method to corrupt him. This made Steven turn into a Corrupted Gem, and he then fled back to Beach City, which he tried to make out a living. He runs into a few friends, including Sadie Miller and Lars Barriga at the Big Donut, trying to feed himself despite having no mouth, and he eventually wanders back to the Prime Kindergarten, where he meets Peridot face to face. While there, he activated the Warp Pad, and ended up in the Crystal Temple, where he was found and he remained as his memories of his older self slowly came back to him.
As he stayed there however, Jasper then arrived to face them, and while he was placed inside the Beach House, he managed to get out and join the fight, although he ended up captured. He did manage to escape and fight Jasper as the others got back to Earth, only to be found by Sombra again. Steven managed to get out and found Sombra in Beach City, which he found against until Peridot arrived. Once Sombra was defeated, he ran back to The Lighthouse, where he fought against Tirek. When all of the danger had passed, Steven was brought to Rose's fountain, and tried to heal himself in the water. It wasn't until Flint and Jade became Nephrite that he was fully healed and back to normal.
After playing with Lapis out in the water one night, Steven falls asleep and during his dream, he was then contacted by the dream being, Lucid. In the real world, this placed him in a hibernation state, which not even Jasper's strong hits could wake him up from. During his travels through the Dreamscape, he is shown numerous passed events from his mother Rose Quartz, including her first being created, the Lunar Sea Spire, and during the first attack on Blue Diamond. It was during this first attack that he is transformed into a Ruby, and actually "fuses" with Sapphire to become Garnet, though he doesn't realize he was a Ruby until later on. While seeing Rose and Pearl's conversation about the rebellion, he finally meets Lapis Lazuli, and comes across Lucid directly. Afterwards, he was placed as Ruby again, and played out a sort of "marriage" scene with Sapphire as one of Lucid's puzzles, before finally coming across at the edges of Limbo. He was almost tricked to crossing over to Limbo by him wanting a picture of his, but he out-smarted him and flew it over to him ala paper-airplane, solving his final puzzle, and finally able to wake up. He stated that while the dream was crazy, it wasn't that bad.
When Garnet made her announcement to them all about their mission to Homeworld, he was more than eager to go and give it a try, getting to work on the Galactic Ray in little time at all. During his work on the project, he took some time to show Connie his friend, Diopside, and after seeing her fight off some seagulls, he gets the idea to have Pearl train her to become a swordsman. This went well at first, but Steven eventually found out from Flint the dangers in this, and Steven raced off to cut the training short, just to find Connie in the middle of one. As he tried to find her, the Eagle Monster arrives and fights him and everyone else. It was during this he vowed to always fight with her, alongside her, and not for her.
As production on the Galactic Ray continued, he showed Greg what he was up to, but unfortunately resulted him in getting "grounded", and not allowed to leave Earth. It took a while, but this problem was eventually resolved just before the ship was complete, and with some convincing and Discord to back him up, was allowed to go with the others.
Homeworld Arrival Arc
Steven and company soon begin to take their leave, and on the way there Steven began to learn about some of Gem culture and some rules to follow to better adapt to Homeworld once they would get there. Upon arrival to Blue Diamond City, he was given a tour of the place by one of Blue Diamond's Era 1 Peridots, and once that was over met with her directly. He was quickly identified as Rose Quartz, but he quickly tried to insist that he was not there for any malicious intent, Blue Diamond not blaming him for what his mother did, much to his relief. During his stay he was shown some Quartz training by Amethyst, Ruby, and Jasper, though finding out that Quartz train with eachother, and not with other types.
When it came time for the duel between Jasper and Rupee, Steven remained supportive of the event, but once Kyra got involved, he quickly intervened before he could fight Yellow Diamond, protecting her despite previous actions. During the event of the Osicone, Steven was left behind for his own safety, but despite the warnings tried to catch up with them anyway. As he went, he came across Yellow Diamond's palace, finding Yellow Pearl with a cracked gem, to which he promptly healed before figuring out where Kyra was. He tried to help him out, but was found by the Osicone, and almost killed before the Crystal Gems arrived and defeated it. He, amongst the others, became heroes of Homeworld shortly afterwards.
Once arriving back home, Steven told the remaining Gems about his adventures on Homeworld when Twilight gave him some information about Neippon, and he was allowed to go with Garnet's permission, alongside Diopside, Peridot, and Connie, in order to help the Mane Six with the Kirin Empire. Upon arrival, they were told of the situation about an Umakumo by Shinrin and Firudo, and soon he was brought into the village and met with the current ruler Junsui. Agfter not getting a lead there, he got a guide to the main cave by Ion and started to search for the Umakumo, managing to figure out the mystery though and saving the day.
He continued his spring aiding the ponies in his own way and doing his own thing, including meeting the Cutie Mark Crusaders, preparing Ponyville for Cranky Doodle and Matilda Doodle's wedding, and helping Pinkie Pie with Velvet Sugar. During one of these days, he went with Peridot, Ruby, and Sapphire to Bayburgh to figure out what Emerald's life was like. He also went with his dad at the end of the season to go to a motel for a week trip, avoiding the Time Jumper incident altogether.
On the one-year anniversary of Lapis's joining of the team, Steven and Connie ended up fusing together in order to first make Stevonnie, marking the day as also Stevonnie's birthday. Sometime after this however, this news was brought over back to Connie's parents, Priyanka Maheswaran and Doug Maheswaran, and Steven had to try and explain to them what fusion was all about, which however didn't go so well. This almost gets him forbidden from seeing Connie until a Gem monster arrives and he and Connie fuse into Stevonnie to defeat it, saving their lives.
He took a trip off to Neippon again to check in on the Kirin Empire, discovering that there was a problem going on at Darastrix, which he and a few others decide to help his problems, in spite of Kyra's insistence for them to mind their own. During a fight with Porath, and his insults to Amethyst, he encourages Amethyst to continue fighting, saying she's perfect the way she is. This ends up bringing them to fuse and form Smoky Quartz for the first time, winning the fight with Porath.
Sometime later, Steven was reminded of his first mission failure when he stumbled onto the Moon Goddess Statue, finding out that it actually was a test after all. This prompts him to go on his first solo-mission, which resulted in mixed reactions from the others. Steven eventually goes to a notable location, and at first went fairly well, but went downhill when a Mountain Lion attacked him, and his food stolen by a pine marten. When he does find the Gecko Monster, he then found it extremely hard and eventually ends up stumbling into the location of Quetzalcoatl, who tells Steven that even the strongest need help once in a while, and relying on friends isn't a sin. This similar idea continued when Steven discovered that his friends have a "Gem Cold", and he had to find the Healing Crystal from the Uktena in order to save them.
During one of his more casual days, Steven enters Lion's pocket dimension to store a shirt when he accidentally releases Bismuth from her bubble inside. He explains this to the other Gems, and eventually brought her out into the limelight, figuring out some interesting details from her. He goes to the Barn House with the newer Crystal Gems, and advised them to stay out of the way until Bismuth was more comfortable, and on a trip to The Forge however, Steven agrees with Amethyst that something wasn't right with her, and also agreed to keep an eye on her just in case. He eventually found out her Gem War involvement, in particular how she poofed Lapis and consequentially got her trapped in the first place, and his worries grew when Bismuth presented him with the Breaking Point. Steven tries to convince her that this was a bad idea, only to get attack for "being a traitor". He was only saved when Quetzalcoatl came back and got him to reveal what was truly going on. Sometime after this, he tried to make amends with Lapis and Bismuth himself, notably during the Hearts Warming Eve event, though not getting too far with it.
Steven became apart of the big mission to save Sapphire from the White Diamond Space Station, put in the position as one of the offerings for the Human Zoo. He, and the other organics were brought to the Human Zoo soon after that and he discovered just how long the Zoomans had been off of their planet, none of them even knowing what that was. Steven was forced to go through the motions until later on, which he discovered a door leading out of the zoo, and his attempts to try it open didn't come to fruition. He was saved however by some of the Crystal Gems, and he tried to rejoin the rest of them. His run to escape however lead him to the Science Lab, where he was captured by White Diamond herself under the crimes of his mother. It was when he was brought to the throne room when he discovered the truth behind the Gem War, and that Rose killed Pink Diamond, to which Steven tries to deny in anger. This escalated into an all-out brawl until they were challenged to a duel, in which Steven was fused with Amethyst and Connie to make Earthstone. In the end, Steven vows with Connie that one day they will find a way to save the Zoomans and Zoomares from the Human Zoo.
During the following winter, Steven and his friends were outside watching the stars in the sky. As he was, he found a space pod flying at them, and discovers Navy inside. When finding out about her cracked stone, Steven quickly healed her up before she could attack anyone else, and brought her over back to Twilight's Library, where she explained the situation to them. Steven was told to stay behind with Navy just in case, but this ended up getting him captured by Aredox agates and brought back to their planet anyway, as wanted prisoners. Upon arrival, Steven discovered the Ruby Squad inside, and first met Razor and Cloud Dancer, who he promises will help escape. It did take a while, but eventually he was then found by Bismuth, though he was brought up to Holly Blue Agate herself after being found. He and AJ were put in a escape pod sometime after, and managed to relocate the others once outside the prison. He didn't get back home until after Bismuth got the other prisoners out, and once getting back, helped them back to their own homes.
Steven took some time one morning to talk to Jamie about things, catching him up yet neglecting to tell him what happened to Lapis, worried it will trouble him further. Soon afterwards, he went off to Winter Wrap-Up to help the others when Fulgurite told them about a big hunting mission he and Amethyst had to do, making him excited for such a big task. Amongst these missions included a Scorpion Monster nearby Beach City with Onion's Gang, a Light Creature along with a Tongue Monster within the Beta Kindergarten. They went on other missions apart of this, including figuring out the source of an early winter in Neippon. After that one particular, Steven found that Amethyst thought she was the worst Crystal Gem, and insists that he was the worst one, pointing out his own flaws before Pearlis arrived and insisted they come to Homeworld for a bit in a fighting match, which he actually wanted to lose in. The fight stopped and Steven explained his situation to the Diamond, only for Yellow Diamond to firmly state as a matter of fact that Rose Quartzes are naturally better than Amethysts, much to his dismay.
They continued going off onto different missions, but during this, he found himself crying tears that weren't his own, and also finds Blue Diamond and Blue Pearl by Pink Diamond's palanquin. It was during his conversation with her to help her out that she tells him about The Cluster. One night, he managed to make contract to Malachite during a dream, and Jasper told him where they were, prompting him, Amethyst, Connie, and the Mane six to go to Mask Island to rescue them. He found them fairly quickly, and after some time, turned into Earthstone to finally beat her, and heal her all at once. Steven helped bring Jasper and Lapis back to the barn before he found out where the other Gems went to, quickly confronting the group about The Cluster. As he was there, he suddenly passes out, and found himself inside the Cluster itself. He convinced the Cluster to stay together, and tries to bubble the Gem, with the aid of Peridot and Pearl finally succeeding and waking up back on the surface.
Upon his return, Steven tries his best to help out Lapis Lazuli, who at the time was isolating herself in the Barn House. This lead him to actually go to Homeworld and bring over Blue Diamond herself to cheer Lapis Lazuli up, but even that didn't get her out of the barn house. In time between his attempts, he found out about the chaos Acid and Cyanide had caused, and tries to fix things: stopping the Restaurant War between the Frymans and the Pizzas, and convincing Sadie Miller to stop her stealing ways.
Eventually, he was called in by Onyx and Pearlis to a trial on Homeworld over not only Pink Diamond, but Blue Diamond as well. He was eventually brought forward during the first part of the trial by White Diamond and intimidated into explaining how he exactly did the deed, despite not even being aware of it himself. Oddly, he actually began explaining his own way on how he shattered her, which turned out to be inaccurate and brought on by her "intimidation", much to the trouble of everyone else. Eventually he was sentenced to banishment from Homeworld, and if he were to be found by anyone on said planet will immediately be put to harvesting.
When the fake emergency warning was broadcasted of an oncoming hurricane, Steven helped the ponies get everyone out of Beach City before the supposed storm, but only to find out too late that it was all a trick, which resulted in the Beach City Flooding. He was the only one, alongside Buck Dewey who didn't lose his home in the flood. He didn't figure out the culprits of the disaster until his visit to Griffonstone, which was his first true encounter with Acid and Cyanide. Upon returning however, he, Connie, and Amethyst were hypnotized and caught by Grootslang, used as "entertainment" as he wanted for his prize until they were snapped out of it and fought back. He was only saved when Ammie appeared, being the first witness to her.
After the rescue, Steven was invited off back to Homeworld by Blue Diamond as a thanks, but he was found out by Pearlis and was soon being hunted down for harvesting. Steven tried to get away, and eventually he ended up in the Supreme Kindergarten. He and the others tried to find a way out, and he ended up running into the Off-Colors, and after hearing about them wanted to help, considering them another group of Crystal Gems. After some work, he managed to help them out and brought them to the Barn House.
He tried to give the Off-Colors a good home during their stay, though this wasn't without problems, as he showed them Ponyville, and had to convince Andy DeMayo to let them stay as well. The biggest problem came when an alien was sent down to Earth to capture him. Steven was given the option of either giving up or having the world killed by a drill ready to pop the bubble he had made, and faced with a do or die scenario, he gave himself up to her. He was saved soon after, but failed to understand what he did wrong, even after Connie left him. It wasn't after he helped with The Ponytones that he found that he betrayed his own promise to Connie to always stay together, and he tried to contact her, only to get nothing. He continued trying over the next few days to contact her, only for nothing to come, and making him feel as worried as he was guilty, thinking that Connie must hate him now, resulting in Pearl confiscating his phone after a while so he could calm down and get his mind off it.
He eventually did get a message, though this could be assumed to be a trap, as he was later seen imprisoned in a White Diamond bubble. He was brought back to the White Diamond Space Station. He was later rescued by Connie, Jamie, Lars, Sadie, and the Onion Gang, just to be caught again moments after release by Aquamarine. During his second imprisonment, he and Connie make up for what happened, Steven apologizing for letting her down. He eventually got out and helped in getting Yellow Diamond and Blue Diamond free from being hybridized, before running to the Sun Incinerator.
White Diamond Arc
Steven was one of those who was "requested" by White Diamond to go with the Diamond Authority on a vacation throughout the cosmos, under the illusion that he was the true Pink Diamond. Throughout his trips to Heiligdom and later Farid, Steven made it his own mission to teach White Diamond all about friendship, as he believes that she doesn't truly know since she had to grow up by herself.
When they crash landed onto Orthix, Steven decided to venture out with Connie Maheswaran to find their friends left outside, using his gem bubble to not be effected by the fog. He did manage to find, but by the time he got back he found everyone effected by White Diamond. Angered, he tried to explain everything to her, trying to both save his friends and get through to her that her way of thinking is wrong. Eventually he eventually managed to get through to her, and while she broke down, tells her that if she can let everyone be whoever they are, then she can let herself be whoever she is as well.
After the successful work done on their vacation, Steven and company called in back home and revealed that he and Pink Diamond had worked out a big celebration for all of Homeworld in the form of a grand festival to celebrate the return of White Diamond, and the beginning of Era 3. During the festivities, he brought the Off-Colors to Homeworld and introducing them to White Diamond.
Steven became more of the main focus throughout the arc. When Grogar came to take over, he tried to convince him to stop but found it very unsuccessful, to the point when he actually tried to kill him after he corrupted Connie right in front of him and was laughing about it. After losing Homeworld, Steven made the ultimate decision to go on and learn how to fight from Jasper. The training itself was successful, but overtime Steven began to grow more and more prone to violence, more so after Grogar confronted him a second time and gave him a scar on his face. He only got even more angered when Nichrome poisoned him, and trapped himself within his own mind, forcing him to break his way out, losing his eye in the process.
By the time the big escape mission played out, Steven had to stay behind with the others but grew more and more worried, wanting to go in himself to save Connie. He reached his breaking point when he heard about the time of the wedding (which was midnight that night), him going as far as to attack Garnet in order to go into Tambalon himself, potentially sabotaging the entire mission. He managed to find Connie inside just before the wedding could finish, confronting and challenging Grogar to a duel for all of Homeworld. He and Connie both go in as Stevonnie for the fight. By the end though, finding Garnet "killed", he ran away.
A week after leaving Beach City, Steven went traveling and eventually found himself in in the Fairfax State, where he stumbled upon Onion and Vidalia. At first he didn't want anything to do with them, believing he was too dangerous to be around, but he agreed to stay with them until he got better anyway, sharing a room with The Dazzlings in spite of his doubts. He stayed with them for a few days, but eventually he was brought to a Ski Resort. During their visit there, he and the others were attacked by a Phase Spider, which during the fight knocked Sonata Dusk unconscious. Believing that he killed someone again, Steven ran out only to be captured by the Phase Spider shortly afterwards. In its attempt to teleport away, he ended up dropped off by mistake, being teleported to Pink Diamond's Garden and upon realizing he was alone, ultimately decided to stay there, feeling it was better this way. After an encounter with Red Diamond while there, Steven changed his mind and returned to Earth, telling Vidalia he was ready to return home.
Upon arriving back, the first person he found was Connie Maheswaran, and upon learning of Grogar's return attack on Beach City, finally realizes that all of his anger and willingness to fight was out of his obsession with Grogar. He and Connie agree to fight, but for themselves and not for him, confronting him as Stevonnie, and later Sunstonnie. During the fight, Steven ultimately saves Grogar's life, coming to terms and actually forgiving Grogar for what he did even if Grogar refused his forgiveness.
Throughout much of the season, Steven Universe took it upon himself in the form of a "Happily Ever After" list to try and fix everything going on: He helps Spinel regain her memory by bringing her to Pink Diamond's Garden; he takes the time in bringing The Dazzlings back with him to make them a new home; while the group was split thanks to Hessonite, he went off to try and find Pearl in The Reef, and even tries for a brief time to reform Grogar after learning more about his tragic past.
He joins the Harmony Gems in both the following court session to get Discord and White Diamond's magic back, and the final main battle between them and Grogar's Army shortly afterwards. Just before the main battle in the Realm of Corners, he joins the original Crystal Gems and Elements of Harmony to take out the weapons located on Homeworld, and tells Spinel to stay behind to help the others before leaving, promising that he will come back. While going through Homeworld, they got caught by Grogar and forced into fighting him. He became the last one left when everyone else gets killed and he snaps and asks why his powers weren't coming back, believing that everything he's going through with Grogar was the story of his whole life. Grogar tells him that this is the fate of all hybrids to suffer, and questions him why he thinks he could change anything, which ultimately makes Steven realize the first power he ever had just before getting thrown down into the Supreme Kindergarten. Despite this, Steven not only survives the fall but regains all of his powers back, and uses them to bring all of his friends back to life. He joins them all in stopping Grogar's advances from Homeworld. After that, he discovers Grogar's backup plan and Sumu invading the planet, and he decides to go and face the creature himself over not only to keep everyone else safe, but also because he was running from Red Diamond's instructions for too long. In the end though, he lets Connie Maheswaran and Spinel go with him to stop Sumu. When going in there though, Grogar was waiting for him, and Steven decides to finally confront him in a one-on-one fight.
Steven regains consciousness as he hears Connie call out for him, he wakes up and looks down at his navel, to see that his gemstone is not visible, leaving him human and slowly dying. Steven takes a couple of steps towards Pink Steven, but then he falls because he is extremely pale, weak, and in pain. With help from Spinel and Connie, Steven continues walking and is given to his Gem half. As Steven laughs and hugs his Gem counterpart, Pink Steven does the exact same thing, embracing each other with joy. The two begin to dance before recombining into Steven, once again, becoming the half Gem-human hybrid he's always been. After reforming, he goes over to Sumu's core, and heals her of Grogar's corrupted curse. After healing the world, he and everyone else go to find Grogar, and Steven tells him when asked about his future, that Steven will be absolutely fine and he's happy no matter what the circumstances because he has his memories of his friends.