In 2016, Salesforce brought onboard Quip, a phone-first word processor positioned as a competitor to Microsoft’s Office suite.

At the end of 2009, Salesforce bought GroupSwim, a company it turned into Chatter, basically a Facebook for the workplace-quite like Microsoft’s Yammer. For years Salesforce has been setting itself on a collision course with Microsoft over the fast-growing and highly lucrative “cloud” market. Like Amazon continually adding new perks for Prime subscribers-same-day delivery, exclusive music, Whole Foods discounts-Salesforce is looking to offer an ever-more compelling bundle-one that might, it hopes, rival Microsoft.

Slack’s chat app is a sticky piece of software that has essentially become an operating system on which offices run, enabling integrations with all sorts of other tools (including Salesforce’s). Slurping up Slack would expand and deepen Salesforce’s virtual hooks into workplaces. He wants to build a platform-that word Wall Street-wooing techies love-to accommodate all offices’ computer-based needs. Why would Salesforce be interested in Slack? Marc Benioff, Salesforce’s billionaire founder and CEO, clearly wishes to build his business into something greater than just a purveyor of software for managing customers and sales leads, the company’s bread-and-butter money-maker. Neither Salesforce nor Slack responded to Fortune’s request for comment. That figure represents Slack’s market capitalization in recent days-before M&A rumors sent the stock surging almost 25%, causing stock markets to halt trading of its shares, on Wednesday. The two tech companies recently held talks about a deal whose value would likely top $17 billion, the Wall Street Journal reports. Salesforce is eyeing what could become its biggest-ever acquisition: Slack, the workplace instant messenger.

Slack sold to salesforce