The real lattice is described at the left, the reciprocal lattice is described at the right. g is the reciprocal lattice vector. The absolute value of g is equal to 2p/d and the direction is that of the normal N to the appropriate set of parallel atomic planes of the real lattice separated by distance d. Two parallel planes of the three-dimensional lattice are shown below.
Colored lines and arrows, the yellow spots.
If you got lost
The animation can be envisaged as follows:
Imagine yourself to be an atom... ( Dah! ) When you fly around the crystal formed from two parallel 7 x 7 planes, you would see the picture at the bottom. If someone watches you from above and tries to figure out what you are seeing, he would draw the pictures at the top of the screen. One picture is a the real image, the other is an imaginary picture "encoded" according to the transformation rules described.