Cleisthenes was an ancient Athenian statesman often referred to as the "Father of Democracy." He lived in the 6th century BCE and is best known for his political reforms that laid the foundation for Athenian democracy. His changes included the reorganization of the political structure, allowing greater participation of citizens in governance. One of his significant reforms was the introduction of the demes, which were local units that helped to decentralize power. Cleisthenes also established the Council of Five Hundred, which allowed citizens to propose and debate laws, further promoting civic engagement and political equality in Athens.