This book presents the functions and mechanisms of macropinocytosis, an actin-driven endocytic uptake process. Key points, including the evolutionary origins of macropinocytosis and major signaling pathways that regulate this uptake mechanism, are highlighted. A wide-array of functions of macropinocytosis are described, including cellular metabolism, cell death, cell migration and antigen presentation. Macropinocytosis has recently been recognized as a critical pathway in disease pathology and treatment. Therefore, a broad overview of macropinocytosis will benefit clinicians, as well as translational and basic research scientists. Moreover, as one of the main clathrin-independent endocytic routes, compiling all the critical information about macropinocytosis in one collection, this book will also be helpful to educators and their students.