Friends, this is a brief note on the Structure and functions of Mitochondria. I have tried to provide very brief account on this for the student who is revising Physiology topics on Cell physiology. To my surprise sketchy and very brief information is available in Standard Textbooks of Physiology as it is considered to be the topic of Biochemistry or Cell biology or Molecular Biology. The information provided is for the benefit of 1st MBBS students appearing in the Subject of Physiology or other undergraduate students of Biology. Hope this will be useful. For detailed account please leave your comments for explanations.