Little is known about the instrument maker whom Galileo appointed to run his laboratory in Padua, beyond the few references in Galileo's papers and scattered archive documents. He was the son of Paolo Mazzoleni and Marietta Bazi, and came from a family of watchmakers. His father and his Uncle Francesco had a thriving artisan workshop in Padua, which came to a bad end because of litagation between the two. While his older brother Mario, a highly qualified scholar, incarnated the family's social advancement and held the chair in Natural Philosophy at the School of Padua for thirty-six years, Marcantonio followed in his father's footsteps and in 1599 was engaged by Galileo, whose home he moved into with his wife and daughter, where he lived for four consecutive years. Afterwards he moved away but continued to work for Galileo at the construction of the most varied instruments, such as geometric and military compasses, set squares, directional compasses, and so on. Even after Galileo returned to Florence, Mazzoleni maintained contact with the University of Padua, and in 1612 took over Father Paolo's post as regulator of the clock of Palazzo del Bo', which houses it, and as "sounder of the bells in unison for the lessons". Though he was a superior craftsman he never became wealthy and in 1615 declared at the revenue office that his only regular income were the proceeds from some farm plots. Galileo held him in high esteem and asked for news of him as late as 1635, with the intention of engaging him for the construction of a compass. But he was informed by Micanzio that Mazzoleni had perished in the plague of 1632.