Actin is a globular protein found in all eukaryotic cells and plays a central role in cell morphology, cell adhesions, cell contractility and motility, signal transduction, transcription and its regulation, cytokinesis and synapse formation, as well as malfunctioning of actin which can lead to various diseases. This book presents topical research in the study of the structure, functions and diseases related to actin. Topics discussed include actin dynamics and remodeling of cell-cell junctions in epithelial morphogenesis; osmotic pressure and the polymeric forms of actin; the molecular mechanisms of actin regulatory proteins and actin cytoskeleton alterations.