This episode is dedicated to the world of twins. We will investigate the unique relationship between them. We will discover that each twin is a person with their own distinct personality. We will show you a sensational film on twin pregnancies, from the first ultrasounds to the birth. We will listen to a series of real-life testimonies from pairs of twins of all ages and from all over the world. Alberto Angela tells us the extraordinary story of the Dionne twins, Canadian quintuplets born prematurely in 1934 in a small village in Ontario. They were identical and so small that each of them could be held in the palm of the hand. Until that day, around thirty cases of quintuplets had been recorded in America but no newborn had ever managed to survive beyond the fifth day. Even in Italy we have witnessed multiple births like that of the famous Giannini twins in the 1980s.