This book chapter give an overview of natural and synthetic polymeric moieties consumed for developing hydrogels and their types. Different properties of nanogels are the advancement of hydrogels characterized by nano-size range, stimuli-responsive swelling, and release. Stimuli responsiveness is imparted by the presence of a suitable monomer. A number of polymerization approaches are presented in the literature that are employed to prepare such networks. These systems are elastic, rubbery, nontoxic, and biocompatible and offer prolonged release of the drugs without chances of dose dumping. These types of networks have potential pharmaceutical, agricultural, food, and biotechnological applications in terms of controlled, prolonged, and targeted drug delivery, solubility enhancements, stimuli-dependent intelligent drug delivery, such as contact lenses, wound healing, etc. In the current chapter, we have tried to introduce hydrogels and microgels, their different types, the variety of polymers used to develop such carrier systems, approaches to develop such drug delivery systems, and their utilization in various sectors in addition to the pharmaceutical sector.