Thermal cameras see heat rather than light, revealing warm and cold spots invisible to the eye. Once bulky and costly, compact thermal imagers now attach to or build into phones and tools, bringing heat-sensing to home and trade use.
They help find draughts and missing insulation, trace overheating electrics, spot plumbing leaks and work in darkness. The images are lower resolution than ordinary photos and interpreting them takes some understanding, so they show patterns of heat rather than fine detail, but having an affordable way to see temperature has opened up many practical everyday uses.