Early life and career
Nicolas Steno was born in Copenhagen on New Year's Day 1638 (Julian calendar), the son of a Lutheran goldsmith who worked regularly for King Christian IV of Denmark. He became ill at age three, suffering from an unknown disease, and grew up in isolation during his childhood. In 1644 his father died, after which his mother married another goldsmith. In 1654–1655, 240 pupils of his school died due to the plague. Across the street lived Peder Schumacher (who would offer Steno a post as professor in Copenhagen in 1671). At the age of 19, Steno entered the University of Copenhagen to pursue medical studies. After completing his university education, Steno set out to travel through Europe; in fact, he would be on the move for the rest of his life. In the Netherlands, France, Italy and Germany he came into contact with prominent physicians and scientists. These influences led him to use his own powers of observation to make important scientific discoveries.
At the urging of Thomas Bartholin, Steno first travelled to Rostock, then to Amsterdam, where he studied anatomy under and lodged with Gerard Blasius, focusing on the lymphatic system. Within a few months Steno moved to Leiden, where he met the students Jan Swammerdam, Frederik Ruysch, Reinier de Graaf, Franciscus de le Boe Sylvius, a famous professor, and Baruch Spinoza. At the time Descartes was publishing on the working of the brain, and Steno doubted Descartes's explanation of the origin of tears as produced by the brain. Invited to Paris by Henri Louis Habert de Montmor and Pierre Bourdelot, he there met Ole Borch and Melchisédech Thévenot who were interested in new research and in demonstrations of his skills. In 1665 Steno travelled to Saumur, Bordeaux and Montpellier, where he met Martin Lister and William Croone, who introduced Steno's work to the Royal Society.
After travelling through France, he settled in Italy in 1666 – at first as professor of anatomy at the University of Padua and then in Florence as in-house physician of Grand Duke of Tuscany Ferdinando II de' Medici, who supported arts and science and whom Steno had met in Pisa. Steno was invited to live in the Palazzo Vecchio; in return he had to gather a cabinet of curiosities. Steno went to Rome and met Pope Alexander VII and Marcello Malpighi, whom he admired. On his way back he watched a Corpus Christi procession in Livorno and wondered if he had the right belief. In Florence Steno focused on the muscular system and the nature of muscle contraction. He became a member of Accademia del Cimento and had long discussions with Francesco Redi. Like Vincenzo Viviani, Steno proposed a geometrical model of muscles to show that a contracting muscle changes its shape but not its volume.