Non-ionizing radiation is electromagnetic radiation that lacks sufficient energy per photon to remove bound electrons from atoms or molecules, thereby preventing ionization. As a fundamental concept and interdisciplinary research domain, it investigates the generation, propagation, interaction with matter (including biological tissues), measurement, and potential effects of this lower-energy class of radiation, which includes radio waves, microwaves, infrared radiation, visible light, and certain ultraviolet frequencies. Its significance lies in its pervasive presence in natural and technological environments, necessitating study of its diverse applications and non-ionizing biological interactions distinct from the effects of high-energy ionizing radiation like that produced in nuclear processes.