Modern Art is based in realism.
When George Seurat painted his first piece of Pointillism (paintings made of dots) portraying realism with a technique never used before; he achieved a break from the way in which paintings had "ever" been made before. His works and the works of his friends were almost real but more like emotional Impressions rather than photo-like as had been the way. You see, in the late 1800's the camera had begun to play an important role and artists grew more inventive. These "French Impressionists" had "abstracted" reality. Although we find their works quite realistic, this was not the case in the Paris of their day. It took years for their talents to be recognized.
By the early 1900's the camera had taken so much portrait painting work away from young artists, which was an essential means of financial support, that again French artists moved even further away from "photo-realistic" depictions. Georges Braque invented a way for paintings to show more of any person, place or thing than any camera can. He painted real things broken or divided into pieces and was able to depict the front, back, top, bottom, inside and outside all at the same time in one painting.
At a Paris exhibition an art critic disliked Braque's new invention so much that he mocked a painting of a French country village. He said it looked like many tiny cubes and mockingly named the style "CUBISM" in his newspaper column.
The name stuck and by the 1920's Cubism was becoming widely accepted. The style gave birth to modern architecture and the whole realm of Art Deco. Now the final great invention of modernism grew out of Cubism. Expressionism was born when the drawing beneath the paintng was done in a more simplified way, some say almost childlike, and that simplicity was visible in the finished painting.
Textures, tecniques and ideas merged with these modern styles but no matter what the finished work looked like it had it's beginnings in realism. Now paintings and sculpture told much fuller stories and conveyed more emotion than ever before in the history of Fine Art. "In essence" Modern Art has the ability to go far beyond the camera by depicting subject matter and it's emotions in a composition recreated by the artist.