text: In practice, a lot will depend on the available volumetric glassware and microvolume measuring and dispensing devices (pipettes).  \n\nLet C1 = initial concentration (50 micromolar) \nLet V1 = the volume you want to dilute WITH (could be all of your 50 micromolar solution or only a part of it) \nLet C2 = the final concentration (100 nM or 0.1 micromolar) \nLet V2 = the volume you want to dilute TO (the final volume you want to end up with) \n\nThe equation is C1 x V1 = C2 x V2 (we must conserve mass)\n\nYou'll have to choose either V1 or V2, then solve for the other one.