Looking at overall organization of the brain, the cell bodies are collected within the outermost area called gray matter, while the axons project inward through the white matter layer.  Functional MRI can be used to identify the ability of these neurons to communicate with each other.  This is accomplished by detecting the movement of water along these neuronal axons and projecting this activity into 2 and 3 dimensional pictures or models.

Amazingly, these pictures can be generated for individual subjects under a variety of conditions.  Many clinical disorders are subsequent to the abnormal functionality of these communication pathways.  Functional MRI techniques are available for tracing these movements and identifying structural and functional behaviors of the brain tissues.
 

This information was adapted from the work of S. Mori (1999)