For high-school seniors like Skylar—who live in prosperous suburbs, have doting parents, attend good schools, and get excellent grades while studding their transcripts with extracurricular activities—the hardest part of the college application is often the personal essay. They’re typically asked to write about some life-changing experience, and, if their childhood has been blessedly free of drama, they may find themselves staring at a blank screen for a long time. This was not a problem for Skylar.

Skylar is a boy, but he was born a girl, and lived as one until the age of fourteen. Skylar would put it differently: he believes that, despite biological appearances, he was a boy all along. He’d just been burdened with a body that required medical and surgical adjustments so that it could reflect the gender he knew himself to be. At sixteen, he started getting testosterone injections every other week; just before he turned seventeen, he had a double mastectomy. The essay question for the University of Chicago, where Skylar submitted an early-action application, invited students to describe their “archnemesis (either real or imagined).” Skylar’s answer: “Pre-formed ideas of what it meant to have two X chromosomes.” No matter what people thought they saw when they looked at him, Skylar wrote, he knew that he “was nothing along the lines of a girl.”

Skylar is an F.T.M., or “female-to-male,” transgender person, a category that has been growing in visibility in recent years. In the past, females who wished to live as males rarely sought surgery, in part because they could “pass” easily enough in public; today, there is a desire for more thorough transformations. Skylar took hormones and underwent “top surgery” at a much younger age than would have been possible even a decade ago. Yet, in his new guise, he doesn’t labor to come across as conventionally masculine. Like many “trans” people of his generation, he is comfortable with some gender ambiguity, and doesn’t feel the need to be, as he puts it, a “macho bro.” He is not sure yet if he will have genital reconstruction when he’s older.

Skylar lives in an affluent, wooded town near New Haven, a liberal enclave where nobody seriously challenged his decision to change gender. Some of his peers even expressed a certain envy. As he explained in his application essay, classmates kept telling him, “This is the most fundamental essence of who you are, Skylar. You can’t possibly get through an entire college application without bringing it up. (Ironically, I haven’t.) This will be your ticket into your dream school.” It was an attitude that irritated Skylar, because, he wrote, “I’ve finally reached a point in my life where my transition is not consuming my life.”

Many trans kids have a very hard time. They are bullied at school, rejected by their families, and consigned to marginal—even desperate—lives. Teen-agers who identify as transgender appear to be at higher risk for depression and suicide. Yet Skylar’s more seamless story is becoming increasingly common. Middle-class parents today tend to actively help their children get settled on a path in life, and often subscribe to the notion that “early intervention” is best for all kinds of conditions. Many therapists have begun to speak of even very young children as transgender (a category that few clinicians of past generations would have applied to them). And plastic surgery, tattoos, and piercings have made people more comfortable with body modification. In such a context, gender surgery in late childhood may no longer seem extreme. Because this change is happening so fast, and amid a flurry of mostly positive media attention, it can be hard to recognize what a radical social experiment it is.

Transgenderism has replaced homosexuality as the newest civil-rights frontier, and trans activists have become vocal and organized. Alice Dreger, a bioethicist and historian of science at Northwestern University, says, “The availability of intervention and the outspokenness of the transgender community are causing a lot more people to see themselves as transgender, and at younger ages.” A recent survey of thirty-five hundred transgender Americans found that, the younger the respondents, the more likely they were to have had “access to transgender people and resources at a young age,” and to have identified as trans at a young age. In a follow-up survey, more than two-thirds of the respondents between the ages of eighteen and twenty-two said that they had known other transgender people before adopting the identity themselves, compared with a quarter of those fifty-three and older.

A kid today who hasn’t met other transgender young people can readily find them in popular culture and social media. Such characters appear on “Glee” (naturally) and on “DeGrassi.” On the Internet, Tumblrs and Listservs and thousands of YouTube videos chronicle the gender transitions of teen-agers. Shot on blurry Webcams in the family basement or in jumbled, poster-covered bedrooms, they variously resemble diaries, instruction manuals, music videos, and manifestos. Last spring, Warren Beatty and Annette Bening’s child Stephen—born Kathlyn—attracted attention after making a video of himself for the site We Happy Trans. Stephen, then twenty and a sophomore at Sarah Lawrence College, explained that, at fourteen, he had “transitioned socially,” adopting his new name and attending school as a boy. His monologue was smart, whimsical, and laden with jargon. “I identify as a transman, a faggy queen, a homosexual, a queer, a nerdfighter, a writer, an artist, and a guy who needs a haircut,” he said. He revealed that he was taking testosterone while “presenting in a femme way,” adding, “It’s nice to finally be able to have my identity be legible to people.”

Skylar told me that “the Internet, and the fact that there are resources readily available,” had made a big difference in his decision to change gender. “That makes it much easier for ideas to spread,” he said. “And this is just another idea to be spread.”

In elementary school, Skylar was what used to be called a tomboy. He kept his sandy hair cut short, and wore polo shirts and cargo pants. (I’ll use “he” for the younger Skylar, too. I don’t even know his former name—this was one remnant of his past that he refused to share.) In the early years of grade school, he hung out at recess with the boys who ran around playing real-life versions of video games, though he also had close friends who were girls. Waiters and sales clerks often assumed that Skylar was a boy, and it soon became clear to his parents, Melissa and Chip, that Skylar didn’t want them to correct the misimpression.

Skylar’s family was not the type to disapprove of an insufficiently feminine daughter. Chip is a trim, Yale-educated I.T. consultant; Melissa has a master’s degree in forestry and runs a nonprofit environmental organization. They divorced when Skylar was nine, and though the breakup was painful, Melissa and Chip remain aligned as parents, sharing a cheerful confidence about Skylar and his older sister, Dakota, now a sophomore at Pomona College. “Skylar never wanted to wear a dress,” Melissa said. “What did I care? I’m not going to force my kids to do things that make them unhappy. That’s the last thing I want to do. Obviously.”