Facebook CEO Mark Zuckerberg introduces Timeline for Facebook in San Francisco.
Facebook CEO Mark Zuckerberg introduces Timeline for Facebook in San Francisco. Reuters/Robert Galbraith

At Facebook's fourth annual f8 developers' conference in San Francisco, Mark Zuckerberg unveiled the single feature that will revolutionize the way users will use Facebook. It's called Timeline.

Timeline is the story of your life and it has three pieces: All your stories, all your apps, and a new way to express who you are, Zuckerberg said.

Timeline divides Facebook pages into two columns, where photos, comments, videos, and more display one's own unique life story, all the way down to one's birth. To fill out the experience, users can click on any point in the timeline and add photos from their past, such as their childhood or infancy. In other words, Timeline allows users to scroll through each other's entire lives on Facebook.

The biggest challenge that we had designing timeline was to figure out how to tell all the most important stories from your life on a single page, Zuckerberg said. You don't want to show every little thing that you've ever done because not everything is defining or critical to who you are.

To keep Timeline relevant, Facebook has constructed a unique algorithm that only saves the true life-changing and most interesting moments to the timeline.

The further back you go, the more it'll summarize for you, Zuckerberg said.

While Facebook loads everything to Timeline automatically, Timeline is still completely customizable. Users can create and delete posts, can share them with only specific people.

You have complete control of your Timeline, what you display there, and who can see it, Zuckerberg said.

Timeline also pushes profile pictures to the side, allowing for users to upload a single cover photo, which can better represent who users are. Between the new two-column Timeline design and the ability to endlessly scroll through one's history, Facebook's new profiles look more like personal blogs.

It's like a scrapbook, but it's more comprehensive, it's more organized, and you don't have to spill out photos all over your living room floor, said Chris Cox, VP of product management at Facebook.

Over the last several weeks, Google+ has advanced on Facebook's user base, but competition has much to fear from this new Facebook. Timeline, while being a nifty design choice, allows users create their profiles to truly reflect their lives. By making your entire life available on Facebook, Timeline dramatically increases the cost of leaving its social network. Should you want to join Google+, good luck finding these same comprehensive features.

Zuckerberg also unveiled the Open Graph, a completely new class of apps that allows users to share what they're doing with each other and invite them to join in on the fun.

Half a billion people use Facebook in a single day.