What is voxel?

Most of us familiar with PIXEL or the smallest addressable element in a display device. We bought our cameras and that is the term that differentiate their quality as well as their price.

Look at the picture below for example,

While pixel is used for 2-dimensional (2D) image, the term VOXEL is designated for a 3D image. Take microCT scan for instance, the scanned images seems like typical 2D image but they are not. In CT scan images, all of the slices actually having their width, length and height. This is the reason why the images can be stacked up again to generate a 3D model out of a patient bone.

(Tibial bone, credit to univ-angers.fr)

A voxel is actually the 3D definition of the discussed pixel. It is best defined as volumetric pixel. The picture below explains what is meant by a voxel, a box in blue color.