The water in oil microemulsion or reverse micelle has been used in the past two decades for the synthesis of many different types of nanoparticles. The nano meter sized aqueous cores of the reverse micelle provide an appropriate stabilized environment for the production of nanoparticles of fairly uniform size, through chemical reactions occurring in the core and it also acts as steric stabilizers to inhibit the aggregation of nanoparticles formed. The water in oil microemulsion has been used to synthesize different types of core nano particles (metals, and semiconductors) as well as core-shell/ composite nanoparticles. This article describes the preparation techniques, and the various techniques used to characterize these core and core-shell nanoparticles as well as insights in to the effects of various process parameters on the terminal particle size. A brief review of our modeling work based on stochastic population balance is also presented, which can be used to describe the formation of both core and coreshell nanoparticles. In addition, we have also presented a brief review of the work on the synthesis of anisotropic nanostructures like nanorods and nanowires by templating against surfactant micelles and reverse micelles. Some findings of our work, addressing the engineering issues, such as possibility of reusing surfactant and organic phases are also included in this article.