This book presents a systematic study on the synthesis, characterization, and physicochemical properties of metal, metal oxide, metal-doped metal oxide, ceramic, and carbon-based nanoparticles. Green synthesis, chemical combustion, and microwave-assisted combustion methods are employed to tailor nanoparticle size, morphology, and crystallinity, with emphasis on eco-friendly approaches using plant extracts.Comprehensive characterization using XRD, FTIR, Raman spectroscopy, SEM, TEM, EDAX, TGA, UV-Vis, photoluminescence, and zeta potential analysis provides insight into structural, optical, thermal, and surface properties. The influence of synthesis parameters, metal doping, and γ-irradiation on nanoparticle behavior is discussed.The book highlights multifunctional applications of nanoparticles in antimicrobial activity, antioxidant performance, biocompatibility, and gas sensing. It serves as a useful reference for researchers, academicians, and postgraduate students in nanoscience and nanotechnology.