Jigsaw Puzzles

Here's a scientific one (from Wikipedia) for those who didn't know:

A puzzle [ˈpasl, ˈpʊsl] (Engl. [ˈpʌzl] riddle, confusion) is a mechanical puzzle, more precisely a laying game in which attempts are made to put the individual pieces of the puzzle back together to form a whole. The English word is jigsaw puzzle (“jigsaw puzzles”) because the first jigsaw games were made.

The puzzle was invented in England in 1766 by the engraver and map dealer John Spilsbury (1739–1769). To do this, he glued a map of Great Britain onto a wooden board and sawed it along the border lines of the various counties. The player had to try to complete the map again. Jeanne-Marie Leprince de Beaumont already used map cuts for didactic purposes. John Spilsbury sold his puzzle as a "teaching aid to facilitate geography teaching". The parts were not yet interlocked as is usual today. These so-called interlocking puzzles only emerged in the second half of the 19th century.