Near- and mid-infrared observations
Incandescent light bulbs shining bright red, or yellow, depending on the temperature. Dust grains get very hot when sunlight shines on them, making them glow in different colors at near- and mid-infrared wavelengths.
Technical definition
Astrophysical observations of celestial objects using telescopes that can detect radiation with wavelengths between approximately 2 and 20 micrometers.