This document discusses solid lipid nanoparticles (SLNs), including their advantages over other drug delivery systems, various preparation methods, sterilization criteria, and characterization techniques. SLNs are submicron colloidal carriers composed of physiological lipids that can encapsulate drugs and deliver them in a controlled manner over long periods of time while protecting drugs from degradation. The document outlines several preparation methods for SLNs, such as high pressure homogenization, and their characterization involves measuring particle size, zeta potential, surface element analysis, and assessing crystallinity. Finally, the document notes applications of SLNs for sunscreens, anti-tuberculosis drugs, and gene delivery.