This book describes the preparation of poly(vinyl alcohol) (PVA) and poly (N-vinyl imidazole) complex nanogels in PVA aqueous solution. This article describes briefly the hydrogel definition, classifactions, crosslinked structure of hydrogels and types of polymers used in tailor made hydrogel. It also gives a brief overview of polymeric nanogels prepared from different origins. It covers different methods used for synthesis of nanogels, Different tools used for characterizations of the synthesized nanogels such as spectroscopic analysis, TEM, DLS and particle size analyzer are discussed.on the other hand, swelling behavior of nanogels is briefly presented. Finally this article provides us the use of the synthesized poly(vinyl alcohol) (PVA) /poly (N-vinyl imidazole) complex nanogels as corrosion inhibitors.