In 1921, Picasso's son Paul was born. Due to this occasion, he painted several paintings with his wife and his son on it. Paul was Picasso's only legitimate son. In 1925, he took part in the first Surrealist exhibition in Paris. Between 1924 and 1926, Picasso preferred to paint abstract still lives. In 1927, he got known to Marie-Thérèse Walter. She became his model and mistress. In 1928, he started a new period where he began to make sculptural works. In 1931, he left his wife and moved with his mistress to Boisgeloup. There they lived in a country home. There, Picasso had a room for his sculptures only. Since 1932, he used Marie-Thérèse as a model. During a travel in Spain, he started to use the bullfight as a new topic of his paintings. In 1935, Picasso's daughter, Maïa, was born. At this time, he got divorced from his wife because of the birth of Maïa. In 1936, Picasso got a job as director of the Prado-Museum in Madrid. During this time, the Spanish Civil War started. German bombs fell on Guernica in Spain on 26 April 1937. Picasso used this impact to paint one of his most famous paintings, Guernica. This painting was completed in about 2 months. It was first shown in the Spanish Pavilion in Paris in 1937.