Mitochondria are not just another organelles in the cell, Mitochondria are the Fundamental Organelles. They provide Energy for all functions and are the Center of all types of Metabolic Pathways, and finally, they determine the Life& Death of a Cell by generating ROS and by controlling Apoptotic or Necrotic Death pathways of a Cell. Mitochondria are as infinite as genes, and in many respects to study mitochondrial functions is a much more difficult task than to study genes. In this book I share with the Reader some of my experiences in solving problems and pitfalls I have encountered during my studies of mitochondrial functions.