Servetus (also known as Miguel Serveto) was the first person to describe the circulation of blood from the heart into the lungs where it was oxygenated before going to the rest of the body.

Servetus' birthdate is uncertain, because he tried to mislead his accusers when he was on trial for his life in Geneva in 1553. Experts believe he was born on September 29, 1511, in Villanueva in northern Spain. Both of his parents, Antonio Serveto and Catalina Conesa, were nobles. He was educated at a church school, and then, at 15 years of age, he became an assistant to Juan de Quintana, a powerful Franciscan friar who later became the confessor to Charles V, the Holy Roman Emperor.

Servetus was very argumentative and stubborn, and he became involved in the bitter religious controversies that divided Europe. He went to Switzerland with Quintana, but then left in 1530 and moved to Strasbourg...