For centuries, people have turned their gaze to the stars and wondered why we are here and whether we are alone in the Universe. We tend to wonder why plants and animals exist, where we came from, who our ancestors were, and what lies ahead. Even if the answer to the main question of life, the Universe and everything in general is not 42, as Douglas Adams once claimed, it is no less brief and mysterious - mitochondria. They show us how life arose on our planet. They explain why bacteria reigned there for so long and why evolution likely did not rise above the level of bacterial mucus anywhere in the universe. They provide insight into how the first complex cells arose and how earthly life ascended the ladder of ascending complexity to the heights of glory. They show us why warm-blooded creatures arose, shaking off the shackles of their environment; why men and women exist, why we fall in love and have children. They tell us why our days in this world are numbered, why we grow old and die. They can tell us the best way to spend the twilight years of life, avoiding old age as a burden and a curse. Mitochondria may not explain the meaning of life, but at least they show what it is. Is it possible to understand the meaning of life without knowing how it works?16+