Hellenistic Greek Sculpture
At the end of the 400s BC, Greece, and especially Athens, was devastated by a terrible war which involved nearly all the Greek city-states, the Peloponnesian War. The end of the war left the Greeks too poor for much sculpture, but when people did begin creating new sculpture again it was in a new style. There is more emotion, especially sad feelings like grief. There is more interest in women, who are sometimes shown without clothes now. Portraits of individuals also became more popular.
Lysippus was another famous Hellenistic sculptor, the favorite sculptor of Alexander the Great. His most famous work is the Apoxyomenos, of a young man scraping the oil from his skin with a strigil (a scraper). It was carved around 320 BC, a little after the death of Alexander. But this work, originally made out of bronze, now survives only in a Roman version in marble.
To find out more about Hellenistic sculpture, check out these books from Amazon or at your library:
Hellenistic Sculpture, by R.R.R. Smith (1991). Not for kids, but a good straightforward approach.
Art in the Hellenistic Age, by J. J. Pollitt (1986). This is more theoretical than Smith's book, and might be harder going. It is more about why Hellenistic artists worked the way they did, rather than just a list of what they made.