A process for preparing nanocapsules having a core-shell structure, comprising:(a) preparing an oil-in-water emulsion by emulsification of an oily phase that comprises a core material, in an aqueous phase, under high shear forces, wherein one or both of the oily phase, and the aqueous phase comprises a sol-gel precursor； (b) subjecting the emulsion obtained in (a) to a high pressure homogenization to obtain a nano-emulsion； and (c) applying conditions for hydrolyzing and polycondensing the sol-gel precursor to obtain nanocapsules having a metal oxide shell encapsulating the core material, said nanocapsules have a particle size distribution of: d10=10-80 nm, d50=30-200 nm, and d90=70-500 nm, in diameter. The invention also relate to nanocapsules having the above particle size distribution and to composition comprising the nanocapsules.
