Far-infrared radiation (FIR) is a type of electromagnetic radiation with wavelengths longer than visible light but shorter than microwaves, typically ranging from 15 micrometers to 1 millimeter. It is part of the infrared spectrum and is often associated with heat, as it is emitted by warm objects, including the human body. FIR is commonly used in various applications, such as in infrared saunas for therapeutic purposes, as it can penetrate the skin and promote relaxation and improved circulation. Additionally, it plays a role in thermal imaging technology, helping to detect heat patterns in different environments.