Measuring time with high precision has led to many hi-tech advances, an impressive one being the GPS. At the heart of every clock is a cyclical phenomenon: from the orbit of the Sun to the oscillations of a pendulum, our solutions have evolved with us. A pendulum, however, is neither precise nor reliable, since it is strongly influenced by its environment. This is why scientists learnt to control highly regular, natural oscillators: the atoms. Atoms only become excited when they absorb light of a specific frequency. By cooling and trapping them with lasers, scientists can measure that frequency and monitor time with unmatched precision.