This book explores the green synthesis and structural characterization of selenium nanoparticles using Moringa peregrina leaf extract, revealing their potent anticancer, antioxidant, and antibacterial properties. Dr. Samer Y. Al-Qaraleh presents a compelling fusion of nanotechnology and plant-based science, supported by advanced analytical techniques (UV-Vis, FTIR, XRD, SEM, TEM). Bridging sustainable innovation and biomedical potential, this work offers fresh insight into eco-friendly approaches to modern therapeutic challenges.