The background to the realistic art found in the Norton : Classical Greek Sculpture

Lysippos was a Greek sculptor of the 4th century BC, says Wikipedia. Together with Scopas and Praxiteles, he is considered one of the three great sculptors of the Classical Greek era, bringing transition into the Hellenistic period.

Notable: his large workshop, the demand for replicas of his work in his lifetime[1] and later among Hellenistic and Roman connoisseurs, the number of disciples directly in his circle,[2] and the survival of his works only in copies.

Among the works attributed to him are the so-called Horses of Saint Mark, Eros Stringing the Bow (of which various copies exist, the best in the British Museum), Agias (known for a marble copy found and preserved in Delphi), the similar Oil Pourer (Dresden and Munich), the Farnese Hercules (which was originally placed in the Baths of Caracalla, although the surviving marble copy lies in the Naples National Archaeological Museum) and Apoxyomenos (or The Scraper, known from a Roman marble copy in the Vatican Museums).
Herma bust of Alexander, Roman marble reflecting an original by Lysippos (Louvre)

Born at Sicyon around 390 BC Lysippos was a worker in bronze in his youth. He taught himself the art of sculpture, later becoming head of the school of Argos and Sikyon. According to Pliny, he produced more than 1,500 works, all of them in bronze. Commentators noted his grace and elegance, and the symmetria or coherent balance of his figures, which were leaner than the ideal represented by Polykleitos and with proportionately smaller heads, giving them the impression of greater height. He was famous for his attention to the details of eyelids and toenails.

His pupil, Chares of Lindos, constructed the Colossus of Rhodes, one of the Seven Wonders of the Ancient World. As this statue does not exist today, debate continues as to whether it was cast bronze or hammered of sheet bronze.