This book concerns two subthemes, 'temperature sensing' and 'temperature-responding systems', addressing the questions of how temperature is sensed and how temperature is related to biological functions, respectively. Temperature affects various physiological functions and is one of the most important factors in homeostasis. The book seeks to integrate our understanding of temperature-dependent biological phenomena with the development of techniques that detect and regulate local temperatures in cells and organs with high resolution and precision. Part I: “Temperature sensing” addresses temperature sensing mechanisms by focusing on plasma membrane molecules, intracellular molecules and intracellular metabolic pathways. This part seeks to develop ways to detect and regulate local temperatures at a cellular level, which would facilitate future temperature- sensing research. Part II: “Temperature- responding systems” focuses on the neural circuits that integrate information concerning ambient temperature sensation, the effects of temperature on metabolic functions and biological rhythms, and mechanisms involved in emotion formation. This part clarifies crosstalk between temperature-responding systems by developing methods to detect and regulate local temperatures in organs. Authors of this book are leading researchers investigating temperature-sensing mechanisms across a wide range of biological responses from molecular to whole organism levels. The book promotes an integrated understanding of temperature-dependent biological phenomena under a novel discipline, 'thermal biology', which leads to a novel concept wherein 'temperature' as a physical quantity could be viewed as an element of new signaling mechanisms.