Its possible the negative white regions that are seen each side of the main black region are being formed from within the spot. (landscheidt.info)
Sessler and colleagues at Pharmacyclics in Sunnyvale, California, found that cancer cells appeared as bright white regions on MRI scans even several days after a texaphyrin injection. (sciencemag.org)
The testis occur as white regions along the body of the animal which is here removed from its calcareous shelter (middle image). (creaturecast.org)