This book provides a general introduction to nanogels, and designs of various stimuli-sensitive nanogels that are able to control drug release in response to specific stimuli.Nanogels are three-dimensional nanosized networks that formed by physically or chemically crosslinking polymers. They have highly interesting properties such as biocompatibility, high stability, particle size adjustment, drug loading capability and modification of the surface for active targeting. They can respond to stimuli which results in the controlled release of drug and targeting of the site.