The Medici commissioned the best talent for the family church and burial chapels: Brunelleschi for the church and Michelangelo for the chapel intended to memorialize their most illustrious princes. 

Both artists died before finishing the work, but Brunelleschi's church was completed according to his plans. 

Michelangelo's chapel, called the New Sacristy, was not; in fact, it was never completed at all. But what he did finish is considered one of the world's crowning achievements in marble sculpture