Final answer:
Pablo Picasso is the painter who pioneered abstract art and Cubism, notably with his painting Les Demoiselles d'Avignon which marked the conception of the Cubist movement.
Step-by-step explanation:
The painter who experimented with abstract art and Cubism is a. Pablo Picasso. Picasso is recognized as one of the most influential artists of the 20th century, having co-founded the Cubist movement alongside Georges Braque. Between 1906-1909, during his African period, Picasso produced Les Demoiselles d'Avignon and other paintings that incorporated primitivist elements, influenced by African artifacts and the Post-Impressionist work of Paul Gauguin.
His experimenting with Cubism involved stressing basic abstract geometric forms and presenting subjects from multiple angles simultaneously. This innovative approach to visual representation marked a significant departure from the linear perspective that had dominated Western art for centuries. Indeed, his work Les Demoiselles d'Avignon (1907) is considered a revolutionary step towards Cubism, influenced in part by the angular surfaces and mask-like forms of African art.