There are 27 of these, one of which is hidden in the middle of the cube, and 6 more of which (the centers of the faces) are probably never referred to at all. The rest of them move about the cube freely, to our great consternation.

An individual colored piece of the cube. There are 26 cubelets on the 3x3x3 cube, 56 on the 4x4x4, and 98 on the 5x5x5. On the 3x3x3 and 5x5x5, six cubelets remain fixed (except for rotation) on the faces of the cubes. The rest of the cubelets move about the cube freely, to our great enjoyment and consternation. 3x3x3 cubelets 8 corners 12 edges 6 middles 4x4x4 cubelets 8 corners 24 edge pieces 2 of these make an "edge" 24 middle pieces 4 of these make an "middle") 5x5x5 cubelets 8 corners 36 edge pieces: 12 edge-middles, 24 edge-edges 1 edge-middle and 2 edge-edges make an "edge" 54 middle pieces: 6 middle-middles, 24 middle-edges, 24 middle-corners 1 middle-middle, 4 middle-edges, and 4 middle-corners make a "middle" 1 middle-middle and 2 middle-edges make a "middle-3-row" 1 middle-edge and 2 middle-corners make an "edge-3-row"