The concept of the wristwatch goes back to the production of the very earliest watches in the 16th century. From the beginning, wrist watches were almost exclusively worn by women, while men used pocket-watches up until the early 20th century. The first watches were strictly mechanical, driven by clockwork. As technology progressed, mechanical devices, used to control the speed of the watch, were largely superseded by vibrating quartz crystals, producing accurately timed electronic pulses. The first digital electronic watch was developed in 1970. Watches are also a fashion accessory, sign of prestige, are variously decorated as jewelry and are subject to changes of fashion.