In the past decade, colloidal solutions have been assumed to be very efficient templates for controlling particle size and shape. A large number of groups have used reverse micelles to control the size of spherical nanoparticles. This makes it possible to determine the various parameters involved in such processes, and demonstrates that nanoparticles can be considered to be efficient nanoreactors. However, some discrepancies arise. There are few reports concerning the control of particle shape, and it is still rather difficult to determine the key parameters, such as the adsorption of salts and other molecules, and the synthesis procedure. Here, we discuss these controls of the size and shape of inorganic nanomaterials.