Many of the world’s most common processes and interactions are governed by the laws of thermodynamics and mechanics. While the transfer, release, or absorption of heat often accompany chemical reactions or seem inherent to mechanical systems, they are also familiar to anyone who has ever spent time outdoors on a warm day or touched a hot plate. Likewise, any physical body—large or small, solid or fluid—is subject to a wide range of forces that trigger motion. This detailed compendium explores the foundations and laws of both thermodynamics and mechanics as well as the lives of those individuals who helped advance these fundamental areas of physics.