A couple of months ago, you could start making Skype calls from within Slack, an award-winning work chat app that's pretty popular with a lot of companies (we certainly use it over here in the Engadget office). Now, however, voice calls are simply baked into the app itself, without you having to use an external service. The feature is in beta right now, and testing will roll out in Slack's desktop apps as well as in Chrome. The voice calling feature actually comes from Slack's acquisition of Screenhero over a year ago.
If you have it, you'll spot a phone icon at the top of your screen next to the info button. Click it and you can initiate a voice call much like most other chat apps out there. This doesn't work with just individual folks either; you can also make channel-wide calls with up to 15 folks, but this is only for Slack users who pay for the service. And because this is Slack -- known for its wide range of emoji -- you can also respond to voice chats with one of several colorful reactions imposed over your user icon.
This isn't to say that Slack will stop supporting the aforementioned Skype or other voice chat services; it's just another option. We should also note that rival Hipchat has had voice and video chat for awhile now. Still, for loyal Slack users, this is great news; here's hoping that video support will be coming too.