It is difficult to overstate the contributions the ancient Greeks gave to Western civilization. A few of their important contributions include the development of history, literature, and philosophy. The Greek historian Herodotus--most famous for his Histories--has been nicknamed the "Father of History" for his commitment to discerning the truth about the stories the Greeks believed about their history. Thucydides, another Greek historian, pioneered the interpretation of history as a series of political events.
The Greek poet Homer birthed Western literature with his epics, the Iliad and the Odyssey. These works remain among the most significant in history and influenced later authors such as Virgil, Dante, Shakespeare, and Milton.
Finally, one cannot study philosophy without engaging with Greek philosophers such as Socrates, Plato, and Aristotle. Each of these men sought to find truth through moral, theoretical, and/or natural philosophy.