In this review, the recent achievements in the synthesis of inorganic M nanomaterials inside the spatially confined volume of individual micro-and submicroreactors (emulsions, micelles, organized thin films, polyelectrolyte capsules, etc.) are presented. The advantages and shortcomings of each type of microreactor are discussed. Particular attention is paid to polyelectrolyte capsules as confined microreactors with controlled shell permeability and the possibility of shell engineering on the nanolevel, thus tailoring different functionalities. Nanomaterials synthesized inside a confined multifunctional microreactor have several advantages: i) absence of particle aggregates, ii) amorphous or metastable crystal phases, and iii) unique composite inorganic/inorganic and inorganic/organic structures.