The stylistic development, architectonic quality, and expressive content of Luca della Robbia’s earliest tin-glazed terracotta sculptures are considered in relation to the sculptor’s close collaboration with the Renaissance architect Filippo Brunelleschi. Luca’s experimentations with humanist subjects and his unconventional ornamentation of vault surfaces are also explored by examining the artist’s relationships with three Florentines: the artist Michelozzo, the humanist Nicolao Nicoli, and his patron Piero de’ Medici. It is in his Labors of the Months (1445-60), commissioned by Piero de’ Medici, that the changes in Luca’s style, technique, and production appear. This cycle, a turning point in his career, led to the creation of his distinctive tin-glazed terracotta ceiling (1462-66) in the Chapel of the Cardinal of Portugal in San Miniato al Monte, Florence. Lastly, a discussion of his process shows that in the fifteenth century Luca’s clay body and glaze chemistry are unique to his bottega, and that they represent an outstanding technical achievement in composition and application.