Hat
From Brickipedia, the LEGO Wiki.
A hat is a plastic lego piece thet can be many shapes and sizes. It represents a minifigure's hat. Connects with the head to make the "top part". They also include the wigs and have been around since 1974.
[edit] History
Hats were first available in 1974 when Minifigures were first intrudected. There was red hats and wigs until the classic Minifigures. 1975 is when Top hats, Doctor hats (White), pigtails, and cowboy hats. Then, 1977 is when intain hats were introduced. 1978 is when you see castle, town and space an bring new meaning to Hats.
[edit] 1978 Onwards
After 1978 brought of all the kind you see now. Some hats make a minifigure like Stormtrooper hats.

