Morphology is a branch of biology dealing with the study of the form and structure of organisms and their specific structural features. This includes aspects of the outward appearance (shape, structure, colour, pattern, size), i.e. external morphology (or eidonomy), as well as the form and structure of the internal parts like bones and organs, i.e. internal morphology (or anatomy). Evolutionary morphology embraces the “how” of morphology, such as the mechanics of how an animal can bite into a hard object with extraordinary force without knocking out its own teeth or shattering them. It also embraces the “why” of morphology, retracing the patterns of evolution in features to understand how a few basic morphological patterns gave rise to the stunning diversity we see in groups from molluscs to mammals to plants. The “how” and the “why” combine to reveal the ways in which organismal evolution has transformed structures and promoted novel functions as well as patterns of association between morphological features and either geographic area or habitat.