Four years ago, Michael Ellenberg faced a crossroads.

He knew how to be a TV programming executive, after spending five years at HBO working on shows such as “True Detective,” “Westworld” and “Big Little Lies.” He knew how to be a producer, after working earlier in his career for Scott Rudin and Ridley Scott.

What he didn’t know was how to be an entrepreneur. He wasn’t sure if he had the stomach to start a company from scratch. Today, Ellenberg’s Media Res banner is a wholly independent venture that has three series in production — one of which is Apple’s starry backstage drama “The Morning Show” — and more on the way.

Teaming with Reese Witherspoon and Jennifer Aniston to help launch Apple’s foray into the content business has been heady stuff. But so has arranging health care coverage for his growing roster of employees.

“Until you’ve done it, you haven’t done it,” Ellenberg says. “From the lease on the building to the actor’s trailer to the quality of the script to a small business affairs point, there’s a new problem that emerges on a daily basis. And none of it you’re prepared for. That’s what’s great, because every day is a learning experience.”

Ellenberg, 44, was elbowed out of his post as executive VP of drama at HBO in January 2016 amid a shake-up of the programming ranks. When he considered his options, he sought to find something that would blend the producing chops he’d developed while working on movies with Rudin and Scott and the production and talent management skills he honed at HBO.

Although Apple TV Plus didn’t exist at the time, Ellenberg could see that the TV business was heading into an unprecedented period of expansion, which made the timing ripe for a startup venture. The executive slogged his way through drafting a business plan and hit the road to drum up cash. He ultimately partnered with film financier Bron Studios to help bankroll his vision for Media Res.

In addition to “Morning Show,” Media Res is the studio behind two other Apple TV Plus series: “Pachinko,” a sweeping family saga set in the U.S., Korea and Japan; and an untitled CIA officer drama to star Brie Larson. Media Res has about 20 staffers, all at its Hollywood office.

“Michael understands quality storytelling and has an ability to attract the best talent in an era of premium series,” says Zack Van Amburg, Apple’s co-head of worldwide video. “He has an ability to understand various perspectives brought by actors, writers, directors and his network partners. That’s a rare quality, and has given him a jump-start in successfully launching Media Res.”

“Morning Show” became quite a calling card for the company once Witherspoon and Aniston signed on. The initial spark for a program set behind the scenes of a network morning show came from Ellenberg’s love of NBC’s “Today” as a kid and his memory of being angry after longtime co-anchor Jane Pauley was forced out in 1990.

“When the show became terrible after that, I remember being fascinated about how you could take something that was so good and make it so bad,” he says.

At the time he was putting Media Res together, Kelly Ripa and Michael Strahan were making headlines because of Strahan’s April departure from “Live With Kelly and Michael” for a full-time role on “Good Morning America.” That real-life drama turned Ellenberg’s attention to the morning show arena, which led him to option “Top of the Morning,” Brian Stelter’s book about another “Today” anchor meltdown, the 2012 ouster of Ann Curry.

Ellenberg had a relationship with Witherspoon after working closely with the actor-producer on “Big Little Lies.” After she and Aniston committed to what would become “Morning Show,” he had no trouble lining up pitches at HBO, Netflix and other premium players in June 2017.

At the time, Van Amburg and Apple Worldwide Video co-head Jamie Erlicht had been on the job only a few days. Ellenberg felt a kinship with the former Sony Pictures Television executives as all three were in business-launch mode. Witherspoon and Aniston agreed that in this case, the risk of going with a network that didn’t exist yet was worth it.

Aniston hailed Ellenberg’s “collaborative spirit” and creative instincts.

“Michael is one of those people who gets energized by what he does and the stories he wants to tell, and this energy he brings to the process of producing is infectious,” Aniston told Variety. “Michael’s pursuit of excellence, combined with his creative instincts and collaborative spirit, make him a great producer.”

“Morning Show” had a bumpy start that necessitated a showrunner change early on. Then the #MeToo movement exploded, forcing the storyline to encompass the great reckoning on sexual misconduct that forced Matt Lauer off “Today” and Charlie Rose from “CBS This Morning.”

It wasn’t until Ellenberg sat in the Rita Hayworth dining room on the Sony Pictures lot last year for the first table read of “Morning Show” that he realized how far the company had come in a short time.

“On a basic human level, you want to feel like you’re stretching yourself,” Ellenberg says. “Now we have a mission with purpose to grow and to do so in the service of great artists and great talent.”