What do you know about the hashtag? When did it start, and where have it reached?

The hashtag’s widespread use began with Twitter but has extended to other social media platforms. In 2007, developer Chris Messina proposed, in a tweet, that Twitter begin grouping topics using the hash symbol.

Twitter initially rejected the idea. But in October 2007, citizen journalists began using the hashtag #SanDiegoFire, at Messina’s suggestion, to tweet updates on a series of forest fires in San Diego.

The practice of hashtagging took off; now users and brands employ hashtags to cover serious political events (#Cairo) and entertainment topics (#MileyCyrus) alike.