Huygens is regarded as one of the best known and most influential scientists and inventors of the 17th century. He built the first pendulum clocks. Their principle had indeed been developed before by Galilei but not implemented in practice. Huygens later constructed pocket watches with balance springs and balances.
Huygens was born on April 14 1629 in The Hague.
The watches, built behalf of Salomon Coster, had an accuracy of only ten seconds per day, a level of accuracy which could be surpassed only a hundred years later. Later, he also constructed pocket watches with balance springs and balances.
From 1666 to 1681 Christiaan Huygens lived in Paris and was a founding member of the French Academy of Sciences. During this time he published his famous work Horologium Oscillatorium (1673). It contains important theorems of mechanics (e.g. conservation of momentum, the oscillation period of a pendulum; extension of the point mechanism to the mechanics of extended bodies, etc.).