Rothko stopped painting things in the late 1940s. What he kept was light, color, and a feeling the work was supposed to give the person standing in front of it: joy, ecstasy, doom, tragedy. He arranged two or three soft-edged rectangles on a field and worked the surface until the colors seemed to hold their own weather inside the canvas.

He asked galleries to hang the paintings low, dim the lights, and let people sit with them. The painting was supposed to do something. Not just be looked at.