A tomographic reconstruction of the colon shows the location of large pools of HIV-1 virus particles (in blue) located in the spaces between adjacent cells. The purple objects within each sphere represent the conical cores that are one of the structural hallmarks of the HIV virus. Tomography refers to imaging by sections or sectioning, through the use of any kind of penetrating wave. A device used in tomography is called a tomograph, while the image produced is a tomogram.