As the leader of the People's Republic of China for the better part of 25 years, Mao Zedong is one of the most influential figures in history and was named by TIME as one of the 100 most important people of the 20th century. Building on Marxism and Leninism, Mao put his own spin on Communist political theory in what is now known as Maoism. But his legacy remains a complicated one. In China, where his portrait still hangs in Tiananmen Square, he is regarded as a revolutionary mastermind whose ideas provided the foundation for advancements that helped the nation grow from an agrarian society into a world power. But much of China's current success came with great hardship. Mao's Great Leap Forward and Cultural Revolution are blamed for the deaths of tens of millions, largely due to famine.