Almost immediately after their invention nearly a century ago, atomic clocks became a key enabling technology in many aspects of modern technology. Recent advances have achieved unprecedented precision and accuracy - resolving time at the level nearly 19 digits - analogous to resolving a map of a large city at the level of an atomic nucleus! The Global Positioning System (GPS) is everywhere - from our phones to aviation and cars. However, it is probably less known that GPS and the navigation applications that it supports would not work without atomic clocks. In addition, once at their planetary destinations, space craft have used on-board clocks to measure the atmospheres above these planets and their gravitational fields. Atomic clocks are essential to the recent first astronomical observation of super-massive black holes.