In the course of the late seventh and sixth century, when Greece was experiencing rapid social and political changes, many Greek towns were ruled by tyrants or sole rulers. Often, these men were aristocrats who had seized extra powers, sometimes relying on a group of wealthy nouveaux riches. Although the word 'tyrant' sounds very negative to us, this was not the case in ancient Greece.
Athens was no exception. A class of aristocrats, the Eupatrids, ruled the city and excluded the wealthy nouveaux riches. Moreover, there were social conflicts. One would have expected the rise of tyrant, but instead the Athenians appointed a wise man named Solon as lawgiver (594/593).
He is responsible for several measures: for example, he decreed that no Athenian would be sold into slavery, even if he were severely indebted (a hectemoros), and that magistracies were open to all rich people (diminishing the power of the aristocrats). He also took economic measures and founded the Heliaia, the people's court. The main result was that people for the first time began to define themselves as Athenians.
After Solon had written these laws, he left Athens for some time. He is said to have visited Egypt and king Croesus of Lydia. Later, he returned home, where he was forced to see how Athens got its tyrant: Pisistratus.
Solon is reckoned among the Seven sages.
Plutarch's Life of Solon is available at LacusCurtius. A biography was included in the Lives of Eminent Philosophers by Diogenes Laertius (here).