This book explores the human understanding of heat, from early cultural perceptions to the scientific developments that shaped thermal science. Beginning with historical musings on heat, it traces the evolution of scientific thought from 16th-century Italy to the quantum understanding of heat in the 20th century. The book examines how humans have perceived, measured, and produced heat, leading to a unified concept that has remained constant: "heat flows from a hot body to a cold body''. It serves as an excellent resource for chemists and anyone interested in the history of chemistry and science.