DNA: the most surprising "invention" of nature and evolution, the true director that allows everything that lives to exist. In fact, DNA is the key that opens the doors to our past and allows us to discover a lot about everyone's behavior, on how to protect ourselves with new treatments and medicines, and even on how to unmask a murderer, or manage to reconstruct the appearance of disappeared living beings. Alberto Angela explains why in some areas of the world there are mainly people with light complexions, or almond-shaped eyes, or long-limbed bodies and why, despite all the differences between human beings, it makes no sense to talk about races. And then, diseases, epidemics such as the plague and the exception of individuals with the same DNA: homozygous twins. We also go to ancient cemeteries in search of the deadly microbe responsible for the Black Death to understand if this or other epidemics could return to exterminate humanity.