Preparation of nanostructured materials such as nanoparticles, particulate composites and nano-suspensions is having a growing interest. In the preparation of such materials, replacing polluting organic solvents by environmentally benign compressed fluids or supercritical fluids as solvents has become a neccesity. This technology (mainly CO2-based) consist of single-step bottom-up approaches to produce nanostructured materials alternative to other multi-step bottom-up procedures such as classical crystallization and also to mechanical and high-energy top-down techniques such as extrusion, milling and high-pressure homogenization. They offer extremely high control of process and product properties. Products successfully obtained are nanosized powders, particulate composite materials such as coated particles, solid dispersions or solid solutions and liquid dispersed systems such as nanosuspensions or nanoemulsions. This technology provides value added products such as efficient drug delivery formulations and also powder, dispersion or emulsion based formulations of dyes, polymers and waxes.