The circadian clock is a complex cellular mechanism that controls numerous key physiological processes and maintains cellular, tissue, and systemic homeostasis. Disruption of the clock system influences the immune response and brain functions. Immune activation is closely linked with inflammation, neurodegeneration, aging, and other peripheral and central nervous system-related abnormalities. There is increasing evidence that cellular inflammation affects sleep and circadian rhythms and vice-versa. This book offers a structured overview that focuses on the multi-angle interaction of circadian rhythms, sleep, and inflammatory response in normal or pathological conditions.