The enthalpies of precipitation of calcium carbonate and calcium fluoride in water/sodium bis-2-ethylhexyl sulfosuccinate/n-heptane, water/didodecyldimethylammonium bromide/n-heptane and water/tetraethyleneglycol-mono-n-dodecyl ether/isooctane microemulsions were measured by a calorimetric technique. The results indicate that the energetic state of CaCO3 and CaF2 nanocrystals encapsulated in the aqueous microregions of these microemulsions is strongly different from that in bulk water. Effects due to the smallness of the nanocrystals, interactions between nanocrystals and water/surfactant interfaces and changes of the thermodynamic parameters in nanoscopic water environments are discussed.