Hypoplasia's underdevelopment or incomplete development of a tissue or organ. Although the term isn't always used precisely, it properly refers to an inadequate or below-normal number of cells. Hypoplasia's similar to aplasia, but less severe. It's technically NOT the opposite of hyperplasia (too many cells). Hypoplasia's a congenital condition, while hyperplasia generally refers to excessive cell growth later in life. (Atrophy, the wasting away of already existing cells,'s technically the direc… (More on Hypoplasia)