A formal visual vehicle much in currency during 20th century art, the grid is a geometric construct of squares or rectangles that form the underlying or actual structure of some two-dimensional modern art. Though the meaning of the grid to artists is hard to describe in words, it is more than just a visual armature. In a way, it can be said to represent the modern and postmodern stance of the 20th century; and often seems to inspire almost a reverence, as a symbol of aesthetic purity and integrity, particularly of modernism. Many artists have used the grid; two who come to mind are Jasper Johns (paintings) and Louise Nevelson (sculpture).<br><br>A framework or pattern of criss-crossed or parallel lines. A lattice. When criss-crossed, lines are conventionally horizontal and vertical; and when lines are diagonal, they are usually at right angles to each other. Typically graph paper is a grid of lines. Things which are often gridded: tiles, tessellations, wire screens, chess boards, maps, graphs, charts, calendars, and modern street plans.How many black dots can you find? The difficulty encountered in seeing illusory black dots results from afterimages. This figure is known as a "Hermann grid," named after its designer.