The applicability of a microcapillary system to solution crystallization and polymorphism control of glycine was examined. The precipitated crystals were observed under an optical microscope in the case of 1) spontaneous cooling of a solution droplet on a glass plate, 2) external cooling in a small agitated vessel, 3) rapid cooling using the capillary. With natural cooling and cooling in the small agitated vessel (cases 1 and 2), hexagonal crystals were obtained, while rapid cooling using capillary (case 3) yielded orthorhombic crystals which seemed to be a metastable phase. By cooling the solution using the capillary, extremely rapid cooling was achieved, which is impossible in the conventional agitated vessel, and such cooling resulted in a higher degree of supersaturation, from which metastable orthorhombic crystals were stably obtained.