Cold chemistry is a research field dedicated to studying chemical reactions and molecular processes that occur at extremely low temperatures, typically ranging from a few Kelvin down to millikelvin or even microkelvin. It investigates the fundamental dynamics of molecular collisions, interactions, and reactions under conditions where thermal energy is negligible and quantum mechanical effects, such as tunneling, resonance phenomena, and long-range interactions, become dominant and dictate reaction outcomes. Key characteristics include the precise preparation and control of molecular states, high-resolution spectroscopic and scattering measurements, and the exploration of reaction pathways and product distributions fundamentally different from those at higher temperatures. This field is significant for advancing fundamental chemical physics, understanding chemical processes in cold environments like interstellar space, and enabling potential applications in areas such as quantum information science and precision measurements.