Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with waves that are just longer than those of red light, the longest waves in the visible spectrum, so IR is invisible to the human eye. IR is generally understood to include wavelengths from around 700 nm to 1000 μmInfrared (IR) radiation can be divided into three main regions based on their wavelengths: near-infrared (NIR), mid-infrared (MIR), and far-infrared (FIR).