This book provides updated knowledge on the basic features and mechanisms of cellular aging established since its first manifestation at cellular level 40 years ago. Contributions of genetic and environmental factors, failure of genetic and cellular repair mechanisms, and the epigenetic modifications determine the final lifespan of cells. This book also provides an understanding on how aging mechanisms in mice, a most frequently used model, differ with that of humans who receive better tumor surveillance because of stringent controls on aging mechanisms. It also appraises the use of modern technology for aging studies and its intervention. This book serves as an excellent reading on cellular aging for undergraduate students, researchers and experts of this area.