This chapter contains sections titled: Introduction Natural Biodegradable Polymeric Nanoparticles Synthetic Biodegradable Polymeric Nanoparticles Thermosensitive and pH-Sensitive Nanoparticles Applications of Biodegradable Nanoparticles Other Than Drug Delivery Physicochemical Characterization of Polymeric Nanoparticles Targeting Nanoparticles by Surface Conjugation with Ligands Cellular Trafficking of Biodegradable Nanoparticles Conclusions References