Adipose tissue, or "fat", has become synonymous with obesity. The public discourse frames a desire to reduce or even banish this tissue at almost every turn, with reasons ranging from aesthetics to health improvements. During decades of research into the development of adipose tissue-reducing interventions, there has also been an increasing acknowledgement and understanding of the physiological necessity for adipose tissue. Functional adipose tissue contributes to overall health due to its role in an incredibly diverse array of processes. For that reason, dysfunction in this tissue continues to be linked to a wide variety of pathologies, from infection to cancer and everything in between. In this book, we gather expert input from those currently expanding this field to provide insight into the importance of adipose tissue.