The simple cubic structure exists in nature only exceptionally, but it is frequently a component part of other cubic structures.
There is one atom in every corner of the cube. Each atom in the crystal borders on 6 neighbouring crystals. Because the atom in the corner belongs to 8 neighbouring cells, one cell contains 1/8 of the atom.
The whole cell has 8 corners, therefore it consists of exactly one atom (8x1/8=1). We come to this conclusion if we choose the cell of which the atom is in the centre of the cell.
