from WIKI:

The miniskirt (often hyphenated as mini-skirt) is a skirt with a hemline well above the knees (generally 20 cm—about 8 inches—or more above knee level). The mini was the defining fashion symbol of "Swinging London" in the 1960s.
Credits to all the original posters of the following images

and to

DR. FIKA at Celebutopia and Foro-Total.net