A triangular lattice is displayed, along with two adjacent "planes" of atoms. (They're lines in two dimensions: we call them planes to get used to the three-dimensional language.) The Miller indices for the planes are chosen by typing and entering them in the boxes below the right hand frame. Click the show planes button to hide the planes or to retrieve them. Try typing and entering different (h k) values and check the planes drawn by bravais with the definition of the Miller indices. (Ignore the colored dots on the right for now.)