Salesforce and WeWork are taking their relationship to the next level: They're moving in together.

Salesforce Tower, a 1,070-foot-high skyscraper that will be the tallest and most expensive building in San Francisco when it's completed, has signed on WeWork as a major tenant. The co-working giant will lease three floors for its second headquarters (the other is in New York City), according to Recode. Some space will be designated as WeWork office rentals.

WeWork, a startup that leases trendy, millennial-friendly office space to startups and Fortune 500 companies, has been scooping up real estate after a $4 billion funding infusion from SoftBank. Its $20 billion valuation makes it the most valuable startup in New York.

In April, Salesforce opened the doors of Salesforce Tower to the media for a sneak peak inside.

"It seems like everywhere I am in this city or around the Bay, I can see this tower," Marc Benioff, founder and CEO of Salesforce, told the crowd at the event.

Take a look inside the new $1.1 billion Salesforce Tower.