Tractography is the algorithmic procedure that estimates white matter pathways using directional information from diffusion-weighted magnetic resonance imaging. Tractography produces a sequence of tri-dimensional spatial points called a streamline. A streamline represents an estimate of the link between two anatomically connected brain regions. The image “Charge Carrier” shows thousands of these streamlines. They are colored by the local density of streamlines (low: red, medium: blue, high: white). Transparency is applied following the local density, making dense regions of streamlines appear through sparse regions. In the end, the image shows the estimated connectivity of the brain with emphasis on the density aspect of the streamlines distribution.