The purpose of this introductory chapter is to provide a general survey to readers from various backgrounds about how we have thought about leaf properties related to their interactions with light. For example, questions such as “is it colored because of how light contacts with the surface or because some colors of light are absorbed by particular materials?” These questions aroused curiosity about how the nature of interactions with light influence leaf properties, such as observations of leaf color differences on the upper and lower foliar surfaces or why leaves change color in the fall. Investigations from Aristotle up to the 19th century focused on the causes of leaf color and its variation and how these relate to how leaves function. Finally, we introduce some of the earliest studies on the physical mechanisms for the color patterns observed.