This book presents classical and modern topics in cell physiology, with a focus on the function of nerve, muscle, and secretory cells. The laws of diffusion, electricity, and mass action are explained and applied to elucidate the mechanisms by which cells establish a resting membrane potential, achieve osmotic balance, generate action potentials, initiate secretion, and control muscle contraction. The book is experimentally-grounded but also introduces students to Python, a modern, easy-to-learn programming language with powerful scientific and graphical capabilities. Python programs are used throughout the book to illustrate important physiological principles and results. These programs, the explanatory text, and the exercises at the end of each chapter provide a unique framework for the exploration of cell physiology at a quantitative and mechanistic level.