On his first trip to New York three years ago, Vine star Cameron Dallas learned an important lesson: It’s never a good idea to invite your Twitter followers into your hotel room. It was a cold night, and two of his social-media-savvy groupies — twin girls — had been sending him messages on Twitter saying they were camped on the sidewalk outside. Dallas, 18 at the time, gave them his floor number and told them to come up. But after taking selfies in the hall, the twins stormed his room.

“They were like, ‘Can we watch you sleep?’ ” recalls Dallas. “I was stunned.” He finally had to physically drag them back into the hall. “They were grabbing onto the doors,” he says. “I really had to pull.”

To a degree, today’s new generation of young stars — whether discovered on the big screen or on YouTube — faces the same challenges that Jodie Foster, Anne Hathaway, and Daniel Radcliffe once had to endure as teenage phenoms: How do you navigate personal and professional growth in front of an audience of squealing super-fans who want you to stay exactly the same as when they found you?

Mark Williams & Sara Hirakawa for Variety

But technology has made the world of young Hollywood dramatically more complicated — and so have seismic shifts in the entertainment industry that have changed the way consumers access movies, TV, and music. The film industry’s reliance on comic books and reboots means that most actors get second billing to the popular franchises in which they appear; the real stars of these blockbusters are the characters in the Marvel or DC Comics.

And while in TV, the explosion of cable and digital programming means there are plenty of opportunities to get a show on the air, the range of options means that show will be viewed by a fragmented audience: It’s much easier to be typecast as a one-note character, and much harder to build a Meryl Streep-like career with a depth and range of performances.

The emerging stars in Hollywood are the ones who are willing to adapt. “A lot of them are really proactive,” says veteran casting director Avy Kaufman, adding that she’s seen an increase in young actors who write and direct. “Everyone is promoting themselves in different ways.”

Like most members of their generation, the performers featured in this year’s Power of Young Hollywood issue have proved themselves to be multitaskers and go-getters.

Ansel Elgort, 22, who made it big with 2014’s “The Fault in Our Stars,” channels some of his creative energy into songwriting, and sidelines as a singer and DJ. (When fans ask him for a selfie, he agrees only if they promise to google his new single “Home Alone.”)

Mark Williams & Sara Hirakawa for Variety

Jaden Smith, 18 — in addition to roles in summer tentpoles (like 2010’s “The Karate Kid,” made when he was 12) and on TV (Netflix’s new series “The Get Down”) —has launched a fashion line, MSFTS Republic, and upended traditional gender expectations with his red-carpet fashion choices.

Elle Fanning, 18, has been playing innocent roles onscreen since age 3, but more recently she has morphed into a fashion icon and the muse of crime-thriller impresario Nicolas Winding Refn, starring in his full-blown horror film “The Neon Demon.”

Digital stars must be career jugglersby the time they are old enough to vote — perhaps a result of the influence of the Kardashians (and all their brands) on our culture. YouTube sensation Bethany Mota has a clothing line, as well as a singing career.

Dallas has dabbled in music, too, in the form of the single “She Bad,” released in conjunction with iHeart Radio. And now the Instagram model-turned-Calvin Klein poster boy is shooting a Netflix docu-series and brainstorming about penning his memoirs. “I plan on writing a book on a lot of things I don’t talk about,” he says, suggesting there are aspects of his life that remain off-camera.

The new career paths of the young and famous are markedly different than the traditional ones Hollywood celebrities used to take. Independent films once served as a launching pad for unknown talent, but that’s rarely the case now. When was the last time an indie turned its actress into a household name? It’s been almost a decade since 2007’s “Juno” prominently gave Ellen Page her start.

Mark Williams & Sara Hirakawa for Variety

Instead, young performers’ identities are largely based on what the blogosphere reports about them. Scott Eastwood rose to fame in 2013 based on a Town & Country photo shoot that went viral. But it’s not clear if that momentum can translate to ticket sales. His role in “Suicide Squad” was so minor that Hollywood will have to wait until “Fast 8” and “Pacific Rim: Maelstrom” to get a more complete picture.

The post-TMZ culture is one where a prerequisite to fame is sharing what you ate for breakfast; anonymity is no longer possible. “It’s harder to be an actor in today’s world because of the internet,” says Leslie Sloane, the founder of Vision PR. “Younger actors have to be aware that no matter where they are, someone is watching, and a phone can be pulled out and anything can be caught on video. Unfortunately, that can define you as you move on in your career.”

In the past, even the biggest starlets could go under the radar if they wanted to, emerging occasionally to sign autographs at events. Now they’re expected to manage full-fledged social-media accounts, updating their whereabouts in real time. Only a few years ago, setting up a Twitter or Instagram account was optional, but not anymore. Studio heads have told Elgort that social media is vital to opening a movie. “As a young person,” Elgort says, “you kind of have to have it.”

But unlike Julia Roberts or Tom Cruise, these millennials don’t see hit movies as the primary indicator of stardom. Although his father, Will, defined his career with box office blockbusters, Jaden Smith isn’t driven solely by the wish to sell tickets. Instead, he speaks in terms that sound more like a college freshman who’s undecided about his major: “If you are happy and the people around you are happy and healthy as well,” he says, “then you’re successful.”

Jenelle Riley contributed to this report.