It’s that time of year: the sunlight fades, the air chills, and the chlorophyll dissipates. The trees around Bozeman succumb to these forces and a physical alteration takes place in our woody surroundings. The golds, reds, and oranges come from a basic scientific reaction: the dwindling sunlight and colder temperatures result in the breakdown of chlorophyll—the ingredient that makes leaves green. In response, the trees build up the sugar stored in their leaves, resulting in the wide range of colors we all enjoy.