This book presents a new method for analyzing the structure and function of the biological branching systems of fractal trees, with a focus on microcirculation. Branching systems in humans (vascular and bronchial trees) and those in the natural world (plants, trees, and rivers) are characterized by a fractal nature. To date, fractal studies have tended to concentrate on fractal dimensions, which quantify the complexity of objects, but the applications for practical use have remained largely unexplored. This book breaks new ground with topics that include the human retinal microcirculatory network, oxygen consumption by vascular walls, the FÃ{u8CA1}eus-Lindqvist effect, the bifurcation exponent, and the asymmetrical microvascular network. Readers are provided with simple formulas to express functions and a simulation graph with in vivo data. The book also discusses the mechanisms regulating blood flow and pressure and how they are related to pathological changes in the human body. Researchers and clinicians alike will find valuable new insights in these pioneering studies.