Biophysicists and medical doctors have learned that malfunction of the control layer in cells is responsible for a host of human disorders ranging from neurological disorders to cancers. Most drugs target components in the control layer, and difficulties in drug design are intimately related to the architecture of the control layer. Intended for a broad audience of students and others interested in furthering their understanding of how cells regulate and coordinate their core activities, this overview explains how the cellular control level works. The audience includes students in chemistry, physics and computer science who intend to work in biological and medical physics, and bioinformatics and systems biology. The first five chapters of the book are supply the background and review chapters, after which signaling in the immune, endocrine (hormonal) and nervous systems is explained, as well as cancer, apoptosis and gene regulation