Hydroxyapatite (HA) nanoparticles are a critical material in various scientific and industrial fields due to their biocompatibility, bioactivity, and structural similarity to natural bone mineral. This article provides an overview of the synthesis methods, structural properties, and diverse applications of hydroxyapatite nanoparticles. It also addresses current challenges and future research directions. 1. Introduction Hydroxyapatite (Ca0°(PO4)6(OH)²)...