Behind one of summer's most cherished outdoor traditions lies a surprisingly complex interplay of organic chemistry, heat transfer, and molecular transformation that results in an iconic treat. Those ingredients, in the form we find them – the marshmallow, milk chocolate, and graham cracker – have their culinary birth as a mixture celebrated today on National S’mores Day. The graham cracker’s defining feature is Graham Flour, a whole-wheat flour made by grinding the components, endosperm, germ, and bran separately, then re-proportioning and combining them to create its distinct nuttiness and flaky texture. Of course, too much heat results in ignition and a bitter carbon char. At the end of the day, understanding the chemistry behind the campfire magic only makes the experience sweeter.