Humans emit radiation that is only visible in the infrared spectrum of light. This can be called thermal radiation and our bodies emit it because of our relative temperature. Warmer objects emit more thermal radiation than cooler objects. For example, our sun, the biggest source of thermal radiation in our solar system has a much higher temperature than the human body. This is why we emit a lower radiation and therefore a light only visible in the infrared spectrum. Unfortunately we can’t see it in our day to day lives, unless you have infrared goggles.
There are many applications of infrared technology as well. For example, the United States army uses the technology for night vision goggles. These goggles help solders see enemies’ heat signatures in the night if they’re hidden. It’s also used in remote controls and other wireless devices. In popular movies like The Predator, the antagonist of the movie can only see objects in infrared vision. When facing off against Arnold Schwarzenegger in the pivotal ending scene, Arnold attempts to hide his heat signature from the predator’s infrared vision by applying cold mud on his entire body and thus appearing invisible to the infrared vision. Humans like us can only see in the full color spectrum.