Owing to diverse applications in the field of electronics, optoelectronics and sensors, zinc oxide (ZnO) nanoparticles are attracting considerable attention in recent years. A few sol-gel processes for lab scale synthesis of ZnO nanoparticles have been reported so far. Increasing environmental concerns over chemical synthesis routes have culminated in efforts to develop biologically inspired synthesis processes. In case of ZnO nanoparticles the biological processes are yet to be explored. This chapter deals with sol-gel route to prepare zinc oxide nanoparticles using a biological agent (aqueous extract of Azadirachta indica (Neem) leaf) and provides an insight into its possible applications. © 2014 Nova Science Publishers, Inc.