Often the least among us most inform us. Surely nothing is less than the minute mites that shun the light of day and seek the perpetual darkness of the mantle cavity of a mussel, which is completely buried head down in the mud of a stream or lake. Every aspect of their lives provides clues as to their origins and their travels. Thus these mites reveal lessons to those who ask questions of them-lessons on biogeography, evolution, ecology and conservation. As Darwin contended, "...whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved," these mites not only lived for 250 million years (since Pangaea) on evolving continents moving across the face of the planet but also lived in evolving mussels, which themselves were evolving with fishes and their kind. All these life-forms evolved complex interdependencies that continue to link them even today. Enduring evolving continents and evolving mussels in a swirl of informative chemicals, these mites have radiated into a myriad of diverse types of bodies and behaviors. Their diversity rivals other major groups of organisms and challenges us to understand their feats in order to make sense of it all. Mites of Freshwater Mollusks is an effort to tell the story of these mites.