Materials having the ability to hold water within the voids of acrylic-based polymeric chain are special class materials used for biomedical applications. In the present review, the different therapeutic applications such as drug diffusivity, tissue engineering, gene delivery and pharmaceutical applications of various poly (acrylic acid) hydrogels and nanohydrogels are discussed. Several techniques for the preparation of different nanohydrogels are compared. The Fourier Transform Infrared, X-ray diffraction, Scanning electron microscopy, H-1-NMR and X-ray photoelectron spectroscopy are discussed for the characterization of nanohydrogels. The swelling, mechanical, and rheological properties of nanohydrogels are also described. The combined accounts of preparation, characterization and properties of nanohydrogels along with the description of various biomedical applications may explore an emerging idea in the area of material sciences.