Watches are basically portable clocks that were originally developed in the 16th century, after Peter Henlein invented the mainspring. They tell the time of day or night and come in all sizes and shapes. Some watch designs are plain and simple while others are ornate and even jewel-encrusted. Until the 20th century, watches had analog displays and many clockwork parts. More recent developments include electric watches with quartz crystals and electronic watches with digital displays.