While devices to measure time have existed for thousands of years, the first mechanical clock was created in 725 by Yi Xing and Liang Lingzan in China. This was the first clock to use an escapement mechanism rather than relying on the flow of water to measure time.
The first portable, spring-driven clocks appeared in the 15th century in Germany. The inventor of this design is unknown, but several clock makers began using the technology all around the same period. Christiaan Huygens developed the first pendulum clock around 1656. He also developed the hairspring, a clock spring small enough to make pocket watches possible.