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.
Challenging one of medicine's long-standing beliefs, a team of scientists funded by the National Heart, Lung, and Blood Institute (NHLBI) and the National Institute on Aging (NIA) has found the strongest evidence to date that human heart muscle cells regenerate after a heart attack.hallenging one of medicine's long-standing beliefs, a team of scientists funded by the National Heart, Lung, and Blood Institute (NHLBI) and the National Institute on Aging (NIA) has found the strongest evidence to date that human heart muscle cells regenerate after a heart attack.