Facebook's News Feed, the backbone of the social network, turns a decade old on Monday.
It's hard to think of Facebook without News Feed, which most of the social network's 1.71 billion users first see when they log into the site or open the app on their smartphones.
A 2014 study sponsored by Facebook and conducted by the analytics firm IDC found the average Facebook user checks the site 14 times a day. It's a safe bet many of those visits included time spent in News Feed.
In honor of News Feed's double-digit birthday, here's a look at 10 key moments in its evolution that got it to where it is today.
News Feed Debuts, Backlash Ensues
The curated feed showing what your friends were posting and discussing launched on September 5, 2006 as a central destination so users didn't have browse through friends' profiles to see what's new.
At the time, Facebook had around eight million users. Usage of the site doubled overnight.
However, there was an initial backlash, with an estimated one million users joining "Facebook News Feed protest groups" arguing the feature was too intrusive, showing every little moment such as Lucy friending Ben or that John and Sarah broke up.
Ranked Personalized Stories
Facebook began using an algorithm to show users the stories it thinks they will care about the most. It's a unique recipe the company continues to fine-tune to this day.
Read More: Facebook Feed Update: Here's Why You'll See More of Your Friends' Posts
Artificial Intelligence
Artificial Intelligence plays a big role in how Facebook powers the unique News Feed experience each user sees. Facebook's AI system runs tens of trillions of queries per day to make about six million predictions per second. So if it knows you like cats, expect to see more feline photos.
Making News Feed Real-Time
Initially, News Feed wasn't in real-time. Facebook would instead sweep through all the possible content on user's profiles, rank the stories and then add updates to News Feed about every five minutes.
The Like Button
The "thumbs up" icon launched in 2009, allowing users show their approval for a friend's post, even if they didn't want to comment.
Reactions
The oft-requested dislike button never came to fruition, but Facebook launched a set of reactions globally in February, allowing people to express love and anger or say "wow" or "haha."
Read More: Move Over, 'Like:' Facebook Users can Now 'Love' a Post
Immersive Story Formats
Facebook News Feed has transformed itself into a virtual lounge over the years by adding more video. Features such as Facebook Live and 360-degree photos, which have taken off in the past year, also add to the feeling of being in a virtual room with friends or at the scene of breaking news.
Social Good
Remember the ALS Ice Bucket Challenge? Many of the 17 million Ice Bucket Challenges videos were shared in News Feed, inspiring friends to take the challenge. The fundraiser went viral and raised tens of millions of dollars for the cause.
Safety
From the aftermath of an earthquake in Nepal last year to the Pulse Nightclub massacre in Florida, Facebook's safety check has been a way for people who are in the area to mark themselves safe and, in turn, make sure their friends are notified in News Feed.
Cutting the Clickbait
Facebook announced last month it would crack down on "clickbait" headlines and rank them lower so they're less likely to show up at the top of a person's News Feed — making it a happier place for everyone.