In the past 12 months, Twitter users sent an astonishing 25 billion Tweets and we added more than 100 million new registered accounts. In that time, our team has grown from 130 people to more than 350 today. We're thankful for every Tweet, every account, and every talented employee who has decided to join the Twitter team. This week, we've got some big news to share.

As part of a significant new round of funding with investor Kleiner Perkins Caufield & Byers and existing investors, we've added two new members to Twitter's board of directors. Please join us in welcoming Mike McCue and David Rosenblatt. The experience these new directors bring to Twitter, along with this renewed investment, will help us continue to grow as a company and business.

2010 was one of the most meaningful years since Twitter, Inc. was founded in 2007. We operate on a principle that people are basically good—when you give them a simple way to express this trait, they prove it to you every day. We're proud of what Twitter users have accomplished, we're proud of our work, and we're very proud of our team. Thanks for being a part of this work; it means a lot to us.

In this edition of #Hindsight2010, we reveal the 10 Most Retweeted Tweets of the year.

American TV personality Stephen Colbert (@StephenAtHome) tops the list with a wry Tweet about the Gulf Oil Spill, the year’s biggest Trend on Twitter. To commemorate the honor, Twitter is awarding Colbert --the titan of ‘Truthiness’-- the first-ever Golden Tweet award for the year’s Most Retweeted Tweet. Twitter co-founder Biz Stone personally presented Colbert with the award tonight on The Colbert Report.

Musicians dominated 2010's Most Retweeted Tweets list: Drizzy Drake (@drakkardnoir) took the #2 spot, and Lil Wayne (@liltunechi) came in at #3. Fascination with Justin Bieber (@justinbieber) is still raging: he placed fourth, while pop stars Joe Jonas (@joejonas) and Rihanna (@rihanna) made the list at #6 and #9 with their Bieber-related Tweets. Congrats also go to Lady Gaga (@ladygaga) (#7) and Kanye West (@kanyewest) (#8).

Humor is a key part of the Twitter experience, and the Most Retweeted list reflects the way that people use the service for comedy and parody. A Tweet from the spoof account @alqaeda clocked in at #5, and words of wisdom from @shitmydadsays rounded out the list at #10.

Finally, an honorable mention goes out to everyone’s favorite feline meme, Long Cat (@longcat111, @longcat222 and @longcat333). The three Tweets that made Long Cat extra loooooong added up to one of the Most Retweeted moments of the year. Meow.

What makes a Tweet powerful?

Every day, we are inspired by people using Twitter in unexpected ways to make the world a better place. Powerful Tweets have impact, relevance and resonance. In just 140 characters, you can change the game, make a difference in someone’s life, offer perspective, or bring aid to people in need. In this installment of #Hindsight2010, we honor the Ten Most Powerful Tweets of 2010.

From a cry for help in the woods to a call for aid for a nation, the Most Powerful Tweets tell ten different stories about Twitter’s value in people’s daily lives. At the top of the Most Powerful Tweets list, journalist Ann Curry used Twitter to gain permission for a Doctors Without Borders plane to land in Haiti to assist the earthquake victims. Other powerful moments: The White House connected to Russian President Dmitry Medvedev on Twitter, an injured triathlete used Twitter to save her own life, a parody account defined the discussion about the Gulf Oil Spill, and the Ecuadorian government used Twitter to declare a state of emergency.

To choose the Top Ten Most Powerful Tweets, the Twitter team reviewed Tweets, news stories and international events from the past year. With more than 25 billion Tweets sent in 2010, narrowing the list to just ten Tweets was a huge challenge. The final selections represent the dynamic ways that people use Twitter in the political world, for disaster relief, and to add commentary to news events, sports and entertainment.

From earthquakes and politics to popstars and hashtags, Twitter Trends are a window into what the world is talking about. In this edition of #Hindsight2010, we offer our list of the biggest Trends of the year.

An astounding 25 billion Tweets were sent in 2010. We analyzed all those Tweets to identify the year’s Top 10 Trends, as well as the leading Trends in eight categories: News Events, People, Movies, Television, Technology, World Cup, Sports and Hashtags. Each Trend in the Top 10 list includes multiple related terms, to give the most accurate view of the topics that people cared about most in 2010. (To find out more about how we define and calculate Trends, check out this blog post.)

Top 10 Twitter Trends of 2010
1. Gulf Oil Spill
2. FIFA World Cup
3. Inception
4. Haiti Earthquake
5. Vuvuzela
6. Apple iPad
7. Google Android
8. Justin Bieber
9. Harry Potter & the Deathly Hallows
10. Pulpo Paul

These Trends indicate the things that are most meaningful in our lives. Each day on Twitter, people tweet about news, sports, entertainment and cool new technology--and everything else in between. The list of 2010 Twitter Trends reflects what’s happening in our world, demonstrates the power of turning any event or story into a shared experience, and underscores Twitter’s value as a real-time information network.

Since Twitter first introduced the Trends feature in the summer of 2008, one frequently asked question has been “Why isn’t X trending?” This question has come up around a variety of subjects, from #justinbieber and #adamlambert to #flotilla, #iranelection and #demo2010.

This week, people are wondering about WikiLeaks, with some asking if Twitter has blocked #wikileaks, #cablegate or other related topics from appearing in the list of top Trends.

The answer: Absolutely not. In fact, some of these terms, including #wikileaks and #cablegate, have previously trended either worldwide or in specific locations.

Given the widespread confusion about #wikileaks, we’d like to offer a longer explanation of how we measure Trends on Twitter, and why some popular topics may not make the list.

What is a Trend?
Twitter Trends are automatically generated by an algorithm that attempts to identify topics that are being talked about more right now than they were previously. The Trends list is designed to help people discover the 'most breaking' breaking news from across the world, in real-time. The Trends list captures the hottest emerging topics, not just what’s most popular. Put another way, Twitter favors novelty over popularity (as BuzzFeed noted in a great article & infographic earlier this week).

What makes a trend a Trend?
Twitter users now send more than 95 million Tweets a day, on just about every topic imaginable. We track the volume of terms mentioned on Twitter on an ongoing basis. Topics break into the Trends list when the volume of Tweets about that topic at a given moment dramatically increases.

Sometimes a topic doesn’t break into the Trends list because its popularity isn’t as widespread as people believe. And, sometimes, popular terms don’t make the Trends list because the velocity of conversation isn’t increasing quickly enough, relative to the baseline level of conversation happening on an average day; this is what happened with #wikileaks this week.

One of the most popular features of #newTwitter is the ability to check out photos, videos, and music directly in the details pane. Click on a Tweet with a link to media, and the details pane on the right lets you view embedded media from partners like YouTube, Flickr and USTREAM. You can also hear iTunes song previews and share music with your friends by linking your Twitter account to Ping, iTunes’ new social network for music.

We’re on a mission to give you more great multimedia content on Twitter, and today we’re adding five new companies to bring you independent TV shows, photos, works of art, slide presentations and entire songs, all right inside the details pane. Twitter users can access embedded media from more than 20 partners in total, including these new companies:

blip.tv: Watch more than 50,000 independently-produced Web TV shows.

Instagram: View mobile photos, personalized with Instagram’s colorful filters.

Rdio: When a subscriber Tweets out a song, Rdio members can listen to full-length songs right inside the details pane, for the first time ever. All other Twitter users will hear 30 second song previews.

SlideShare: Read and share entire presentations, directly on Twitter.

Dipdive: See photos, videos and new works from Dipdive's community of artists.

In the next few months we’ll integrate with more content partners. For Twitter users, this means that 140 characters can contain a world of multimedia content, and instantly connect you to video, photo, music and media services all across the Web.

By 2015, that number could be zero. Imagine it -- the first generation of children in 30 years to be born without HIV.

When this disease first began ravaging societies around the world, the Internet as we know it was a mere infant, cellphones cost $4,000 and the idea of an open, global exchange of information with the tap of a few keys was just a dream.

Now, a Tweet can reach millions of people in seconds.

Today is World AIDS Day, and our friends at (RED) are encouraging you to tweet using the hashtag #turnred. It's one small step towards making the dream of an AIDS-free generation in 2015 a reality.

It will take all of us to keep this issue on the forefront of the fight against AIDS to ensure the funding and focus needed to reach this goal continues. Use your Tweet today to start practicing.

When you use #turnred today, your tweet of support will help turn a map of the world red.