A brief review of published papers was done in nanogeochemistry, a new field of geochemistry in which particles and fluids of small size (<100 nm) were investigated. They are different in properties from their larger analogs because of the greater contributions of their surface energy. Conditions, forms, and mechanisms of their formation and evolution were considered. Examples of size dependencies of nanoparticle and nanofluid properties (solubility and stability, melting temperature, inner pressure, surface charge and sorption, rates of evaporation, chemical reactions, and transport) were shown. Different influence of convex and concave surface on properties was noted. Widespread distribution of nanoparticles and nanofluids in nature provides their influence on various geochemical processes. Nanoparticles sorbs heavy metals and are the main form of their transport in natural waters. Nanofluids (nanopors) control the processes of diagenesis, metasomatic substitution and weathering, gas migration in shales. Even with a small content, nanoparticles can change behavior of macro systems dramatically. The main development directions of nanogeochemistry were summarized.