The cell is the basic structural and functional unit of life. Cell physiology refers to the biological study of the various processes that take place in the cell, which keep it alive. In living systems, free radicals such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) play a crucial role in regulating a wide range of cell activities such as autophagy, metabolism, growth and development, solute transport, programmed cell death, and stress responses. Furthermore, ROS and RNS can damage tissues through oxidative stress and tissue dysfunction, and they can also act as molecular messengers for stress responses that are advantageous to the organism. Cellular pathology on the other hand, studies the diseases that occur in the cells, tissues and organs. The primary diagnostic tests that are utilized in cell pathology include cytopathology and histopathology. This book provides an insight into the new paradigms in the research on cellular physiology and pathology. It will serve as a valuable source of reference for graduate and post graduate students.