The first true flowering of Matta's own art came in 1938, when he moved from drawing to the oil painting for which he is best known. This period coincided with his emigration to the United States, where he lived until 1948. His early paintings, give an indication of the work he would continue, with diffuse light patterns and bold lines on a featureless background. 

As Matta’s work evolved, his key ambition to represent and evoke the human psyche in visual form was filtered through the writings of Freud and the psychoanalytic view of the mind as a three-dimensional space. These paintins "are visual analogies for the artist's psyche". 

During the 1940's and 1950's, the disturbing state of world politics found reflection in Matta's work, with the canvases becoming busy with images of electrical machinery and distressed figures.  

In his art Matta creates new dimensions in a blend of organic and cosmic lifeforms, known as biomorphism. He was one of the first Surrealists to take this abstract leap, successfully combining the political and the semi-abstract in epic surreal canvases.