Blue jeans are sturdy pants made from denim, a thick cotton fabric dyed blue with indigo. They were invented in 1873 by Jacob Davis and Levi Strauss, who added metal rivets at stress points to make work pants that could withstand the tough demands of miners, ranchers, and railroad workers.

For decades, jeans were purely work clothes, the kind of pants you'd wear to dig ditches or build fences. But in the 1950s, teenagers started wearing them as everyday casual wear, and jeans transformed from workwear into a symbol of youth and rebellion. Today, people wear jeans everywhere: to school, to restaurants, even to some offices.

Denim's distinctive blue comes from indigo dye, which sits on the surface of the threads rather than soaking all the way through. That's why jeans fade and develop their own unique patterns over time: the indigo gradually wears away with washing and use, creating lighter blue patches and streaks.

People often just call them jeans or denim, dropping the “blue” part since most jeans are blue.