Improvements in spectroscopic resolution have been the driving force behind many scientific and technological breakthroughs over the past century, including the invention of the laser and the realization of ultracold atoms. State-of-the-art lasers can now maintain phase coherence over one second, that is, 10¹⁵ optical waves can pass by without losing track of a particular cycle. The recent development of optical frequency combs permits this unprecedented optical phase coherence to be established across the entire visible and infrared parts of the electromagnetic spectrum, leading to direct visualization and measurement of light ripples. A new generation of light-based atomic clocks has been developed, with ultracold Sr atoms confined in an optical lattice offering unprecedented coherence times for light-matter interactions. The uncertainty of this new clock has reached 1 x 10^-16, a factor of 3 below the current best Cs primary standard. These developments will have impact to a wide range of scientific problems such as the possible time-variation of fundamental constants and quantum simulations based on cold atoms, as well as to a variety of technological applications.