Steno was born in the Lutheran stronghold of Copenhagen during the Thirty Years War, a conflict between Catholics and Protestants that eventually engulfed most of northern Europe. While a toddler, he contracted an illness that confined him indoors for three years, and shortly after he recovered, his father died. Stenos mother soon remarried, but her new husband died just a year later, and the boy went to live with an older half-sister and her husband. When Steno was 15, an age when most kids value their friends the most, he lost many of his; plague struck Copenhagen, and his buddies were recruited to cart away the contagious bodies of the dead. This kind of uncertainty characterized Stenos entire life. He never owned a home, seldom lived in one place for long, rarely enjoyed a steady income, and agonized over the fate of his soul.
Between bouts of despair over his inability to focus on one topic, Steno managed to impress his elders. Spending so much time surrounded by adults during his childhood illness had made him a good listener, and after his father was gone, Steno was happy to listen to surrogate fathers. The first of these was Ole Borch, an alchemist. Steno didnt care much for alchemy, but he remembered what he saw in Borchs workshop, especially solid particles suspended in liquid. Memories of these particles of sediment gradually settling to the bottom of the mixture would help him envision geologic processes in later years.
Steno hoped to study mathematics, but a career as a doctor looked far more practical. He enrolled at the University of Copenhagen to study medicine, yet found himself outdoors sketching snowflakes instead. Even worse, his formal studies stopped altogether when the university closed its doors. Denmark was at war with Sweden, and between military defeats by the Swedes and two punishing winters in a row, the entire city ground to a halt. Steno made the best of a bad situation. Thomas Bartholin, Denmarks leading anatomist, had retired from the University of Copenhagen about the time Steno enrolled, but the men became friends anyway. Steno might have learned good dissection techniques from Bartholin, or simply inherited exceptional manual dexterity from his goldsmith father. Either way, several years after scrounging for firewood in frozen Copenhagen, he found himself in Paris, dazzling Europes glitterati with his skill.