Mold is a type of fungus that grows as fuzzy patches on damp surfaces, and temperature controls how quickly it spreads. In one experiment, bread samples receive water and brown sugar, then sit at three temperatures. The hypothesis is that warmer temperatures will cause the fungi to grow faster.

Temperature directly controls how fast microbes multiply. One bread sample sits under a lamp at about 25 degrees Celsius. Another goes into the fridge at about 4 degrees Celsius. The warm sample grows fungi the fastest, while the cold sample barely changes at all.

Fungi grow best in warm, moist conditions. Cold temperatures slow their feeding on dead matter nearly to a halt. Placing bread samples at different temperatures shows this clearly, since the warm sample grows fungi the fastest.