The earliest recorded clock was invented in 1300 BC in Egypt and was a sundial that used a shadow to indicate the time of day. Over subsequent centuries, various advancements were made including using church bells in France in 1370 and water clocks in Greece in 1400 BC. The first mechanical clock was invented in Europe around 1400 BC using a mainspring and balance wheel. Modern innovations included the first wrist watches being sold affordably in the US in 1886 and the first atomic clock being built in 1949.