The main focus of the book is the preparation and characterization of polymeric electrospun photoluminescent nanofibers (PLNs) and its flexible lightening applications. The book provides an introduction of nanomaterials and their synthesis techniques focusing on two major approaches: Top-Down and Bottom-Up. Several characterization techniques such as X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X- Ray (EDX), High Resolution Transmission Electron Microscope (HRTEM), Photoluminescence (PL) and Raman Spectroscopy have been discussed. The book also focuses on the Electrospinning technique and its parameters in detail. In addition, the text covers the basic concepts of luminescence and fluorescence phenomena on the basis of Jablonski diagram as well as Down-Conversion and Up-Conversion Nanophosphors (UNCPs). The findings of the book are based on the research work of the author.