About Donatello (from Wikipedia):
Donato di Niccolò di Betto Bardi (c. 1386 – 13 December 1466), better known as Donatello, was an Italian sculptor of the Renaissance. Born in Florence, he studied classical sculpture and used this to develop a complete Renaissance style in sculpture, whose periods in Rome, Padua and Siena introduced to other parts of Italy a long and productive career. He worked with stone, bronze, wood, clay, stucco and wax, and had several assistants, with four perhaps being a typical number. Though his best-known works were mostly statues in the round, he developed a new, very shallow, type of bas-relief for small works, and a good deal of his output was larger architectural reliefs.