Who invented the first watch in the world?

Peter Henlein invented the first portable time piece in 1504. The first person to attach a portable time piece to his wrist with a piece of string was Blaise Pascal.

Early wrist watches were only worn by women. Wrist watches from this time period were not as reliable as pocket watches and easily ruined by rain or dirt. Improvements to the design of wrist watches were made at the beginning of the 20th century. During World War I, soldiers wore wrist watches in the trenches. It became fashionable for men to wear wrist watches after the war when the soldiers returned home. Previously, men only wore pocket watches.