Blizzard Entertainment’s Overwatch League, the first franchised esports league, kicked off its inaugural season earlier this year. Twelve teams from around the world compete every week in Burbank, California, at an arena that housed the stages for The Tonight Show with Johnny Carson and Jay Leno.

Blizzard is entering a well-established market. Revenue in esports will pass $900 million this year, according to Newzoo.

Companies like Riot and Valve, who make some of the most popular competitive games, have been holding competitions for several years with prize pools snowballing in the millions. Viewership of esports events hit an all-time high of $46 million in 2017 and investors have taken notice.

The owner of the NFL’s New England Patriots, Robert Kraft, owns an Overwatch League team. Shaquille O’Neal, Marshawn Lynch and Jennifer Lopez are also investors.

The stakes are high for the players and these pro gamers, some of them just 18-years-old, are under constant pressure.

“There’s a lot of mental stress that goes on, and if you don’t have a clear head and you’re not 100 percent focused, that’s going to affect how the coaches see you, how your own teammates see you,” said Andrej “Babybay” Francisty, a player on the San Francisco Shock team.

The team’s training regimen rival that of any other pro athlete, and they are often training twelve hours a day.

“We get one day off. That’s it. And usually on our day off most players are still playing the game,” said Nikola “Sleepy” Andrews.

Each week players compete on a massive stage, and fans can buy tickets and attend like any other sporting event. The whole thing is broadcast live on Amazon’s Twitch to viewers around the world. More than 10 million people tuned in to watch the opening week in January.

“A lot of people think, oh it’s just playing video games. But physical fitness and mental conditioning is a huge part of this,” said Overwatch League Commissioner Nate Nanzer. “They all spend time working with nutritionists, they work on their sleep schedule, all the things you’d expect a high powered athlete in any sport to do, but the training that they do during the day is playing Overwatch.”

The competition will go through July, leading up to the Grand Finals where the top two teams will compete for a one million dollar cash prize. That will conclude the inaugural season, but Blizzard has big plans for the future of the league.

Eventually the teams will host competitions in their home cities, said Nanzer.

“That’s when we think Overwatch League is really going to blow up — when millions of fans around the world to have the opportunity to go engage with the content live,” he said.

“Video games are huge, they’re mainstream, they’re not going anywhere,” Nanzer said. “The debate about whether or not it’s a sport is irrelevant. It’s competition, it’s entertainment. Millions of people love to watch it, and it’s here to stay.”