Slack, the business communication tool and tech darling, has begun rolling out voice calling to users today, reports TechCrunch. The new tool, called "Calls," allows any Slack user to start a private call or conference call with any other Slack user or channel. Slack has previously integrated calling features into its service via third-party solutions like Skype and Google Hangouts, but as TechCrunch notes "those required a separate installation and were quite clunky by comparison" to Slack's new Calls feature.