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A study of the activity of the XVIII century Milanese optician François De Baillou and his family has been carried out. His ancestors migrated from France possibly at the beginning of that century. He became the most esteemed optician of his times in the duchy of Milan and he obtained in 1750 the title of "Regio Cesareo Ottico" from Mary Therese of Austria. He had a brother, Giovanni (dead ante 1763) who worked first for the Duke Farnese in Parma and then in Florence for the Granduke Gian Gastone de' Medici. François had a son, Giacomo, who was also optician in Milan and obtained the same title as his father in 1775. He continued to work after his father's death in 1774. A brief survey of other components of the family is given. Working mostly as a spectacle-maker he made a variety of optical instruments; they were largely advertised on dedicated trade-brochures. Here some microscopes and telescopes are analytically listed together with an account of their technical characteristics.