This book presents a comprehensive history of the precision measurement of physical values. Improvements in time and frequency measurement accuracy have been instrumental to the advancement of physics. Pivotal discoveries in the field, such as the establishment of Newtonian mechanics, have often coincided with the development of more accurate clocks. There remain many questions in modern physics whose resolution would require the measurement of effects too small for our current technology to discern. Before we can solve these mysteries, we must first achieve further reductions in measurement uncertainty.The book charts the fascinating journey from our reliance on the movements of the sun to measure time, to the most recent developments in atomic clocks, reducing measurement uncertainty to 10-18. Along the way, it considers how these advancements have contributed to our understanding of physics, and the role that further improvements will play in the field. All from undergraduate students to industry professionals will find great value in this detailed and insightful volume on the past and future of frequency precision measurements.