This book presents key concepts in the structure and function of vascular smooth muscle cells in health and disease. Supplemental reading may be drawn from the extensive references listed at the end of each chapter. Vascular smooth muscle cell is the major cell type in blood vessels. Dysfunction of vascular smooth muscle cells is an important cause of vascular diseases, for example, atherosclerosis, hypertension, and circulatory shock. Vascular smooth muscle cells are phenotypically plastic, capable of switching between two major phenotypes -- contractile/differentiated phenotype and invasive/proliferative phenotype in response to environmental clues. Chapter 1 introduces the major areas of research presented in this monograph. Chapters 2 to 4 address the structure and function of the contractile/differentiated phenotype of vascular smooth muscle cell. Chapters 5 and 6 address the developmental basis of vascular smooth muscle cell phenotype and structure and function of podosomes (invasive organelles) in the invasive/proliferative phenotype of vascular smooth muscle cell. Chapters 7 to 9 address the role of vascular smooth muscle cell dysfunction in vascular diseases -- atherosclerosis, hypertension, and circulatory shock.