Angiogenesis is the growth of blood vessels from the existing vasculature. The field of angiogenesis has grown enormously in the past 30 years, with only 40 papers published in 1980 and nearly 6000 in 2010. Why has there been this explosive growth in angiogenesis research? Angiogenic therapies provide a potential to conquer cancer, heart diseases, and more than 70 of life’s most threatening medical conditions. The lives of at least 1 billion people worldwide could be improved with angiogenic therapy, according to the Angiogenesis Foundation. In this little book, we provide a simple approach to understand the essential elements of the angiogenic process, we critique the most powerful angiogenesis assays that are used to discover proangiogenic and antiangiogenic substances, and we provide an in-depth physiological perspective on how angiogenesis is regulated in normal, healthy tissues of the human body. All tissues of the body require a continuous supply of oxygen to burn metabolic substrates that are needed for energy. Oxygen is conducted to these tissues by blood capillaries: more capillaries can improve tissue oxygenation and thus enhance energy production; fewer capillaries can lead to hypoxia and even anoxia in the tissues. This means that angiogenic therapies designed to control the growth and regression of blood capillaries can be used to improve the survival of poorly perfused tissues that are essential to the body (heart, brain, skeletal muscle, etc.) and to rid the body of unwanted tissues (tumors).