Overall, we show the synthesis of metal selenide nanoparticles in an in situ process, starting from α-SeNPs. For the first time, complete conversion of α-SeNPs to metal selenides is observed with metals other than Ag. The completeness of this conversion may be due to the smaller size of Se nanostructure used in this work. The reaction appears to proceed through the disproportionation of α-Se. Because the reaction is complete, in situ, and proceeds with α-SeNPs produced both chemically and biologically, the reaction may find use in correlated light/electron microscopy and in flow-reactor based syntheses.