Large, unicellular trichome on the seed coats of Gossypium species are the cotton fibers of commerce. Cotton fibers, as hyper-elongated unicellular outgrowths of the outer integument of Gossypium species ovules, mature through four temporally overlapping developmental processes. Fiber initiation begins three days before floral anthesis and persists until the sixth day post anthesis [DPA]; fiber elongation begins with floral anthesis and continues until approximately 25 DPA. Secondary wall cellulose deposition commences at approximately 14 DPA and continues through 42 DPA, depending on the growth environment. Fiber maturity is reached at approximately 56 DPA under 'normal' growing conditions. The lengths of all four fiber developmental phases are highly dependent upon the growth environment and genotype-related responses to prevailing environmental conditions.