Facebook video chat, free of charge. Thanks, Skype.

It’s a simple formula: the world's largest social network, plus the world's largest video-chat system, equals the world’s easiest one-click way to instantly see your friends.

The Facebook video chat announcement means that its 750 million users will be able to talk with any of their online friends thanks to a new partnership with Skype, which could soon be a part of Microsoft.

“It’s so minimal and so easy to use, I just think a lot of people are going to want to use it,” says Mark Zuckerberg, CEO of Facebook.

After about six months of planning with Skype, Zuckerberg announced the new video-calling feature of Facebook chat at a press conference Wednesday with Tony Bates, CEO of Skype, and other Facebook employees at their headquarters in Palo Alto, Calif. The announcement confirmed one of the many rumors that had been floating around in recent weeks about a new feature that Zuckerberg deemed “awesome.”

In the coming weeks, users will see a small video icon in chat boxes and a “Call” button on profile pages that with one click will launch a ringing noise on a friend’s computer. A window will then pop up, asking the friend to accept or decline the call.

If that friend has never used the video-calling feature, a plug-in can be installed within 10 to 20 seconds before beginning the call, Zuckerberg says.

When a friend accepts a call, a large window will appear in the middle of the screen, which first shows the person making the call (so you know how you look). Then the person on the other end of the call will pop up.

“This stuff is possible because the social infrastructure already exists,” says Zuckerberg, who suggests that the past five years have been about connecting people, but now it’s time to build on top of the existing technology with new features.

“The driving narrative for the next five years is not going to be about wiring up the world,” Zuckerberg says. “It’s going to be about what kind of new stuff are we going to build.”

Adding to the new video-calling feature are two more advances rolled out by Facebook: group chat and a new design.

More than 50 percent of Facebook users are active in groups, says Peter Deng, a product manager at Facebook. People are connecting with each other and want to connect with multiple people at once without the hassle of setting up a group chat beforehand, he says.

With the new multi-person chat feature, a user can chat with one person and then invite other friends within the same chat box. If the friend is online, the message will be received instantly, but if the friend is offline, the message will be delivered to that user's inbox.

The third new feature announced Wednesday is a new design for the chat tab that will take into account a user’s browser size.

“The new chat design includes a sidebar that lists the people you message most,” wrote Philip Su, Facebook software engineer, in a blog post. “Now it's easier to find your friends and start a conversation. The sidebar adjusts with the size of your browser window, and it automatically appears when the window is wide enough.”

The announcement of these three new features “marks the beginning of launching season 2011,” Zuckerberg says.

When asked if the features announced were available for Facebook on mobile devices, he said they are mostly designed for the browser, although group chat will appear the same as a single-person chat on a mobile device.

“We try to do each thing, and each thing really good, and then work on the next thing, which will probably start tomorrow,” Zuckerberg says.