The world’s smallest thermometer is 20,000 times tinier than a single human hair. Oh, and it’s made out of genetic material.

Researchers from the Laboratory of Biosensors and Nanomachines at the University of Montreal state that they have produced a thermometer out of DNA in a recent article in the journal Nano Letters.
DNA molecules spread out as a reaction to heat. So the researchers designed DNA structures that would unfold and fold at very specific temperatures. Thus, the make-up of the DNA strands can show data about the temperature. The thermometer has a range of 122°F. When the temperature attains certain levels, the tiny thermometer sends out light-based signals.

The discovery could one day be used to gauge temperature in nanotechnology or even to observe changes in temperature between individual cells in the human body.