The region of the electromagnetic spectrum located just below the visible portion (i.e., just beneath the red end) of the spectrum, which consists of wavelengths from 780 nanometers (or 0.000001 millimeter) to 1 mm. Infrared radiation is also used as a source of heat, particularly in the drying of certain types of inks (such as super quick-set infrared inks). (See Electromagnetic Spectrum.)