Cleisthenes was a member of the powerful Alcmaeonid family that had been previously exiled by Peisistratus. When the Alcmaeonids returned with a Spartan army to drive Hippias out of Athens, Cleisthenes emerged as the leader. Cleisthenes built on Solon's work and his new laws were unexpectedly not in favour of the nobles. The changes that Cleisthenes made were very radical and must have distressed many Athenians with traditional views. However his political arrangements played a vital role in the development of Athenian democracy which continued to develop after his death.
One of the most major changes that Cleisthenes brought about was the changing of the Athenian tribal system. The population of Athens had always been divided into four different tribes based on ancestry. One tribe consisted of many phratries, which were a clan made up of several extended families, or genos. A genos consisted of a number of oikoi, which were smaller families. Therefore all the members of a tribe were, although often distantly, related.
Cleisthenes redistributed the entire Athenian population into ten tribes, based not on blood ties but on the area in which one lived. His aim was to mix up the people so that a greater number could share in political administration. Also the significance of the four-tribe system was waning as the population of Athens grew and the mobility of the people increased.
Cleisthenes divided Attica into 30 parts (trittyes), of which ten were areas of land near the coast, ten inland, and ten in the polis itself. Each tribe consisted of three parts, one from each section. This meant that each tribe contained people of differing interests and ways of life: those living inland would tend to be farmers, those by the coast fisherman or herdsman, those in the city involved in some kind of industrial work. .
New tribal system changed the way that a man would refer to himself, e.g. instead of the introducing himself as someone's son; he would introduce himself as a man of a certain village.