Microsoft today launched a messaging system for businesses, Microsoft Teams, putting it in direct competition with fast-growing start-up Slack and Facebook's Workplace product.
The new product will be part of Microsoft's Office 365 cloud-based software suite.
Slack, whose customers include CBS, BuzzFeed, universities and the US government, among others, had over 4 million daily active users in October.
The company took out a full page ad in the New York Times today, addressing the entry of Microsoft Teams.
"We're genuinely excited to have some competition," Slack said in the ad.
Microsoft said a preview of Teams will be available to Office 365 commercial customers with enterprise or business plans, starting today.