The earliest Greek literature, which is attributed to Homer and is dated to the eighth or seventh centuries BC, is written in “Old Ionic” rather than Attic. Athens and its dialect remained relatively obscure until the establishment of its democracy following the reforms of Solon in the sixth century BC; so began the classical period, one of great Athenian influence both in Greece and throughout the Mediterranean.
The first extensive works of literature in Attic are the plays of dramatists Aeschylus, Sophocles, Euripides, and Aristophanes dating from the fifth century BC. The military exploits of the Athenians led to some universally read and admired history, as found in the works of Thucydides and Xenophon. Slightly less known because they are more technical and legal are the orations by Antiphon, Demosthenes, Lysias, Isocrates, and many others. The Attic Greek of philosophers Plato (427–347 BC) and his student Aristotle (384–322 BC) dates to the period of transition between Classical Attic and Koine.
Students who learn Ancient Greek usually begin with the Attic dialect and continue, depending upon their interests, to the later Koine of the New Testament and other early Christian writings, to the earlier Homeric Greek of Homer and Hesiod, or to the contemporaneous Ionic Greek of Herodotus and Hippocrates.
Source: Wikipedia