Nanomaterials have emerged as a significant focal point for the scientific and industrial realms, fostering innovative solutions through the precise manipulation of materials at the nanoscale. This chapter reviews recent advancements in the preparation, characterization, and application of nanomaterials, emphasizing their place in medicine, energy, and environmental sustainability. This chapter also discusses various synthesis methods and green and sustainable methods, with the effect of parameters, such as molar ratios, reaction time, and capping agents, on the properties of nanoparticles. Substantial research has been dedicated to nanomaterials' biomedical applications, including targeted drug delivery systems, disease diagnosis, and tissue engineering. The chapter addresses how nanoparticles can go across biological barriers, such as the blood–brain barrier, for treating neurodegenerative diseases and dives into the application of nanomaterials in energy storage and conversion systems, particularly lithium-ion batteries and solar-driven water-splitting technologies. It also addresses applications in environment-related fields, such as pollution control and waste management. In addition, advanced techniques in characterization and simulation in computation have been discussed concerning optimal property behavior and understanding of nanoparticles. Bibliometric analysis indicates the emerging trends and the clusters of research studies in the scientific field, while various case studies demonstrate real applications of nanotechnology in industrial contexts. The chapter highlights the role of the synthesis parameters in achieving desired material properties and looks at grain size performance in an association.