Definition of opacity for English Language Learners. : 1  the quality of a material that does not allow light to pass through it : the quality of being opaque. : 2  the quality of being difficult to understand or explain.
Research has shown that this is not true, and that brain cells can and do regenerate, especially in the areas related to learning, decision-making, visual recognition, and the way people perceive objects in space.weet. For a long time, scientists thought that it was impossible for brain cells to regenerate because they assumed that any new cells would disrupt the order of the brain.
The salamander can regenerate the limb, heart, tail, brain, eye tissues, kidney, brain and spinal cord throughout life. Cross-section of a regenerating salamander limb; Green = limb muscle fibers; Red = skin. Zebrafish can regenerate heart tissue without relying on stem cells.