The history and the styles
The oldest style in Tai Chi is Chen-Style which was only taught in a Chinese village Called "Chen Jia Gou". All the dwellers there were a big family and their last name is Chen. They treated Tai Chi as a secret and don't taught others.
A Young man named Yang Luchan wanted to learn this kung fu so he attended the village and worked for the family. No one taught him but the smart boy learned it by spying the training of the family. At last his sincerity moved the family and taught him all the secret of Tai Chi. The story of "stealing learning" is very famous and the young man became the founder of Yang-Style Tai Chi. After he went to Beijing and taught there, all the northern China was shocked by this kind of kung fu. And he was called "undefeated Yang". About him, there're many legends. People think he could put a bird on his hand, when the bird wanted to fly, it pushed its claw, as soon as Yang feel it, he put down his hand a little bit at the same time so that the bird can never fly from his hand. And one day his teenage son beat a famous master in the first move but tore his sleeve. After he came back, Yang laughed at him," I never heard a opponent can touch a Tai Chi master's clothes, so do you think you've learned Tai Chi?"
Yang and his son's student Wu Quanyou founded the Wu-Style Tai Chi.
Another student of Yang named Li Ruidong, people called him "Nose Li", had some debate with Yang's son and decided to find a way to beat Yang-style Tai Chi. He absorbed the other two "IN-style" kung fu, Xingyi-quan And Bagua-palm, at last developed his own Li-style Tai Chi.
Yang's townee Wu Yuxiang learned Tai Chi from not only him but also Chen Jia Gou and combined them to found the Wu-Style Tai Chi.
Later another gifted kung fu master called Sun Lutang founded Sun-Style Tai Chi. Sun had such a talent that each of the best of the best master would like to teach him. He learned Xingyi-quan from Guo Yunshen, who was said that no one can stand his half-pace-punch except Yang Luchan, Bagua-palm from Cheng Tinghua, the "Glasses Cheng" because of his business, who was the close-door student of Dong Haichuan the founder and was famous of his death, he himself beat down tens of foreign enemies but was shot by guns. And Sun's Tai Chi was taught by Hao Weizhen, the third leader of Wu-style Tai Chi. Sun was very small and got a nickname "living monkey". But when one time he fight with a boxing champion from the west, he beat the opponent out like stuck him on the wall.
So from then on people descript Tai Chi's power as "to beat a person like to stick a picture". He also beat 5 foreign masters from himself lying on the ground after his 70 years old.