The morphology of the $D_2O$-induced reverse micellar structure of an amphiphilic block copolymer of poly( ethylene oxide )-b-poly(propylene oxide )-b-poly( ethylene oxide )($EO_{76}PO_{29}EO_{76}$) was investigated in hydrophobic media by small angle neutron scattering (SANS). Increasing $D_2O$ in the styrene/divinylbenzene solution of $EO_{76}PO_{29}EO_{76}$ led to a change in morphology of the reverse micelles from a short range ordered molecular aggregate to a hexagonally arranged micelle, and further to a spherical micelle.