Takeshi Yokomori is a Japanese combustion engineer and Professor in the Faculty of Science and Technology at Keio University. Specializing in combustion science and thermal-fluid engineering, his research focuses on flame dynamics, combustion control, and energy conversion technologies. His work ranges from fundamental studies of combustion to applications in aerospace, automotive engineering, and power generation, with an emphasis on reducing environmental impact and advancing next-generation energy technologies. In What Is Combustion?, he traces humanity's long relationship with fire while explaining the mechanisms of combustion and modern combustion technologies in an accessible way, revealing the fascinating science behind one of the most familiar phenomena in everyday life.