Micellar solutions of PAAm-b-PEO-b-PAAm triblock copolymer (TBC) based on chemically complementary poly(ethylene oxide) and polyacrylamide (M-n= 6 and 116kDa) were applied to study the encapsulation of poorly soluble crystallizing drug prednisolon (PS) in a region of phi= 0.065 divided by 0.39mol(PS)/base-mol(TBC). The equilibrium mechanism of the encapsulation and the effect of specific aggregation of small and large PS-loaded micelles by their coronas that promoted the drug crystallization were established. The fractal character of large drug-loaded micelles and unusual morphology of PS crystals allowed assuming the presence of TBC micelles inside crystalline space.