U Is for Uplifting: #10YearsofYouTube

Amid the animal hijinks, epic stunts, silly pranks and music videos, sometimes a gem arises that really moves you. It makes you laugh. It makes you cry. It makes you believe in yourself. Something you can’t help but want to share with the world.

While the feel-good factor of a particular story or video is hard to measure, it's easy to sense. Here are four memorable, uplifting moments from the last 10 Years of YouTube:

Randy Pausch's Last Lecture: With months left to live, this beloved Carnegie Mellon computer science professor gives his last lecture -- a 75-minute lesson on resilience, wonder, and powering through hard work in order to live your dreams. He honors the people who have helped him and the people he's helped, and in doing so, inspires with a message that is unforgettable.

Hearing for the First Time: Sarah Churman receives a hearing implant after 29 years of silence, and we get to witness the first time she hears herself speak, laugh and cry. Her joy is a reminder of how human technology can be, and how the everyday things we might take for granted are truly a gift.

Kid President's Letter to a Person on Their First Day Here: Robby Novack, known as Kid President, welcomes new babies into the world through a candid celebration of all the simple experiences that make life worth living. Things like laughing with loved ones or dancing to music. He's also honest about the hardships of getting up in the morning, believing in yourself, messing up, and making friends.

Elderly Man in Nursing Home Reacts to Music: A clip from the 2014 documentary Alive Inside, this video captures the moment a generally unresponsive man with Alzheimer’s Disease reawakens while listening to music in his nursing home. Slipping on earphones, his eyes and smile come alive when he hears his favorite songs. It’s a video testament to the mysterious, magical relationship between music and the human mind.

T Is for Timelapse: #10YearsofYouTube

Nearly nine years ago, an artist named Ahree Lee posted a timelapse video on YouTube called “Me.” The minute-long piece features over a thousand portraits of Lee taken over the preceding three years: all close-ups of her face in nearly the exact same position and with the same expression, cycled through day by day in chronological order.

A New York-based photographer named Noah Kalina discovered Lee’s work and was inspired to transform his own timelapse project into a similar piece of video art. (Coincidentally, he, too, had been photographing himself everyday - but for six years rather than three.) Kalina’s “Noah takes a photo of himself every day for 6 years” became a sleeper hit and earned him one of the first spots in the YouTube Hall of Fame, as well as a feature in the New York Times, a segment on VH1, and an homage by Homer on an episode of “The Simpsons.” The video of Kalina’s 6 year transformation has racked up more than 26M views in its lifetime, and ~7.2 years of time watched.

YouTube’s 1.7M+ timelapse videos have offered us new, eye-opening perspectives on the people, places and things that surround us. From watching the world spin on its axis from 250 miles in space, to witnessing the poignant transformation of a young girl from birth to adolescence, to seeing through the eye of a storm, timelapse videos alter our perception of time and the natural metamorphoses of everything around us in a way never before possible.

Overall, more than 4,400 days (or 12 years) worth of timelapse footage have been uploaded to YouTube, the sum of which has been viewed more than 3.9 billion times. Check out our playlist below for some of our favorite timelapses from the last 10 years.

S Is for Singers: #10YearsofYouTube

Whether professional, amateur or animal; auto-tuned, a capella, or lip-dubbed, singing has proven to be one of YouTube’s most popular forms of entertainment. Of the 250+ channels in the billionaire’s club (aka, those with a billion views or more) more than half are channels featuring singers and songwriters, with one of the most recent inductees being not a pop star or a top record label, but the Eurovision Song Contest, crossing the threshold on March 30.

Eurovision's milestone should come as no surprise: some of the most unforgettable performances on YouTube are not ones made by famous “billionaires,” but those made by everyday people, like Susan Boyle (24 million views), Italian Nun Cristina Scuccia (72 million views), and - once upon a time - a young, unknown phenom from Ontario (48 million views - and now 11 billion subscribers to his VEVO channel).

So here’s to all the performers out there - novice, emergent and diva - that have made the last 10 years of YouTube sing.

R Is for Reactions: #10YearsofYouTube

Where would YouTube be without reaction videos? Kids’ reactions, moms’ reactions, reactions to scary pranks or beautiful proposals. A genre that was once non-existent has grown to become one of the most popular forms of video on the platform, bringing people back for “lols” and “awws” time and time again. In fact, one of YouTube’s earliest viral hits was a reaction video -- the original Scary Maze Prank, which is currently sitting pretty at 27 million views.

Reaction vids have been a YouTube staple for years. But it wasn’t until The Fine Bros React series that the idea hit new heights. Debuting just a few weeks before the fifth anniversary of YouTube’s official public launch, the series began with kids simply reacting to popular YouTube videos. It was a meta moment that proved an instant hit, pulling in more than 10 million views to date. Five years later, the Bros have garnered more than 12 million subscribers and nearly 3 billion views across their 800+ videos.

Still, the most interesting reaction to see has always been your own.

GOTCHA. Because how could we talk about the “R” of the YouTube alphabet without a Rick Roll?! A cultural phenomenon that took off in 2007, Rick Astley’s “Never Gonna Give You Up” still sees a spike every April Fools’ Day, with friends performing this musical bait-and-switch all over the world. In fact, the largest spike in views in the video’s history happened just this past April Fools' Day when the video was viewed over 2 million times. Proof that the Rick Roll is still a sure-fire way to get a reaction out of anyone. See what we did there?