The human brain processes visual information not simultaneously, but in stages, creating the so-called "visual maps." When we look at an object, biologically we do not perceive a complete image at any given moment. Visual perception is sequential. The brain first perceives / processes vertical and horizontal contrasts, i.e., lines. Then it turns to processing contrasting areas of light and dark: this allows us to see shaded areas, and consequently three-dimensional obects and shapes. Then comes the perception of different colors (a "color" map of an object). This adds color to the image that already has lines or contours and shaded areas. Such stage-by-stage perception of visual elements in the brain allows us to use these elements separately in visual art.