The electromagnetic spectrum is many different kinds of electromagnetic radiation wave trains. The spectrum, itself, is a continium. The very long wavelength radiation is the Radio and TV waves that pass through the air continually. They, like most radiation, are invisible to the naked eye and they pass through our bodies without any biological effect since the energy associated with such radiation is insignificant. Radio waves are intercepted from the vastness of interstellar space by Radio Telescopes that reveal the secrets of the universe.
Microwave radiation is another region in the spectrum.
Microwave waves are used in the communication industry and in the kitchen as a way to cook foods. Microwave radiation is still associated with energy levels that are usually considered harmless except for people with pace makers. However, there is some concern that intense microwave radiation have a long exposure time may be harmful in certain circumstances. Moving down to shorter wavelength radiation, there is the infrared region. This region of the spectrum is sometimes called heat waves .