The present invention relates to nano-in-micro particles for intradermal delivery of active substances. The nano-in-micro particles according to the invention comprise a matrix of microparticles and nanoparticles carrying at least one active substance and wherein the nanoparticles are dispersed in the matrix of microparticles. In a preferred embodiment of the invention the nano-in-micro particles comprise a densifier.The invention in particular relates to nano-in-micro particles wherein the nanoparticles carry at least one vaccine and the use of the respective nano-in-micro particles for immunization. The invention further relates to the preparation of such nano-in-micro particles and the use thereof. In addition, the invention relates to compositions comprising these nano-in-micro particles, in particular pharmaceutical compositions.
