Cosimo II was the son of Ferdinand I (see Medici family). He became Grand Duke in 1609. He was a patron of Galileo and appointed him as his personal philosopher and mathematician, along with the title of Professor of the University of Pisa, although the latter without any teaching obligations.
Galileo wanted to dedicate the satellites of Jupiter, later denominated "Medicea sidera", to him, and he also made him a gift of a proportional compass. From 1605 onwards he employed in his service Robert Dudley.