Two common defects of the eyes are myopia (short-sightedness) and hyperopia (long-sightedness). In both cases, rays of light do not focus on the retina so a clear image is not formed. These two ...
Stem cells close stem cellA cell found in foetuses, embryos and some adult tissues that can give rise to a wide range of other cells. can divide to produce new cells, which can then divide into ...
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