Tomography of the human brain

Tomography's main use is in a medical context.

Here is an image displaying multiple cross-sections of a human brain before they are compiled into a three-dimensional image. If you can imagine them each being placed on top of each other, then you'll start to understand a bit better how tomography works

by sending out penetrative rays through a solid object, in this case a human brain, and reflecting them back to a receiver, it is possible to monitor the intensity change of the original penetrative rays. This change of intensity in the rays reflects the density of the surface through which they had to pass at their, and thereby allows the user to build up an image of the plain through which the rays were focused (ie: where all the rays were focused after reflection). These plains, or "layers" are combined to create a 3d image.