The Heliades were three sisters in Greek mythology; Aegiale, Aegle, and Aetheria. Their brother was Phaeton and they were daughters of Helios, the sun god. When Phaeton died driving Helios' chariot, they mourned and grieved so much (4 months) that the gods took pity on them. The gods changed all three into poplar trees. Their arms turned into branches. Their legs turned into a trunk, and their tears into amber. They stayed poplar trees forever. Heliades means "children of the sun".
Ovid II, 340.