Twitter celebrates its seventh anniversary today.

The first ever tweet was sent in San Francisco, California, by Twitter creator Jack Dorsey on 21 March 2006.

Today, there are 200 million users worldwide, according to Twitter.

Journalist and author Kate Bussmann, who wrote A Twitter Year: 365 Days In 140 Characters, said: "It's no understatement to say that in seven short years, Twitter has changed the way the world communicates.

"It's given us all the power to get our voice heard and to connect easily and instantly with other people who care about the same things we do — whether that's politics or sport, Justin Bieber or Downton Abbey.

“It’s made the world smaller.”

Twitter allows users to post messages containing 140 characters or less, though 40 per cent of users do not tweet but use the platform to follow other users.

10 facts about Twitter

- 400 million Tweets are sent every day.

- It took three years, two months and one day for the first billion Tweets to be sent on the platform. The same number are now sent every two-and-a-half days.

- The hashtag (#) feature, first proposed by a user, first appeared on Twitter in August 2007.

- 60 per cent of users Tweet via their on mobile

- The re- tweet feature was launched in August 2009, more than three years after the platform was founded.

- The most re-tweeted Tweet to date was president Barack Obama 's message, "Four more years", after he won the US presidential election on November 6th, 2012. It was re-tweeted more than 811,000 times.

- On March 25th, 2012, James Cameron sent a Tweet from the ocean's deepest point, the Mariana Trench in the western Pacific.

- The first Tweet was sent in San Francisco, California, by Twitter creator Jack Dorsey on March 21st, 2006.

- Today there are 200 million users worldwide

- Twitter was localised in right-to-left languages Arabic, Farsi, Hebrew and Urdu, increasing the number of localised languages to 28, on March 6th, 2012.