Just when I thought I understood the concept of planes and miller indices, I got stuck on a 'test your understanding' Q in my book. I can't understand that there can be two or more (110) planes in a crystal lattice? I thought there can be only one such plane. The question asks me to find the distance between the nearest (110) planes in a simple cubic lattice, with the value of lattice constant given. I can solve the Q, but I need to know if there can be really two (110) planes in a crystal lattice, and where will they be? I discussed it with a few classmates, and they don't get it either. We all agree that there can be only one (110) plane in a cubic lattice. Any help will be greatly appreciated!