Living systems consist of diverse components and constitute a hierarchy, from molecules to cells to organisms, which adapt to external perturbations and reproduce stably. This book describes the statistical and physical principles governing cell growth and reproduction, and the mechanisms for adaptation through noise, kinetic memory, and robust cell differentiation through cell to cell interaction and epigenetics. The laws governing rate, direction, and constraints of phenotypic evolution are examined from the perspective of microscopic units (molecules) and macroscopic states (cells), with a focus on maintaining consistency between these length and temporal scales. By integrating theoretical, computational, and experimental approaches, this book offers novel insights into biology from a physicist's perspective and provides a detailed picture of the universal characteristics of living systems. It is indispensable for students and researchers in physics, biology and mathematics interested in understanding the nature of life and the physical principles it is based upon.