Numerous animal species live in environments characterized by a seasonal reduction in the availability of water, which often but not always occurs when temperatures are highest. For many such animals, survival during the toughest season requires spending long periods of time in a rather inactive state known as aestivation. But aestivation is much more than remaining inactive. Successful aestivation requires the selection of a proper microhabitat, variable degrees of metabolic arrest and responsiveness to external stimuli, the ability to sense the proper time of year for emergence, the preservation of inactive tissue, and much more. So, aestivation involves a complex collection of behaviors, ecological associations and physiological adjustments that vary across species in their type, magnitude and course. This book seeks to explore the phenomenon of aestivation from different perspectives and levels of organization, ranging from microhabitat selection to genetic control of physiological adjustments. It brings together authors from across the world working on different systematic groups, approaches, and questions, but who are all ultimately working to better understand the complex issue of aestivation.