<p>Since the 1990s, solid lipid nanoparticles have been developed as a novel drug delivery system and utilized for delivering various drugs. These nanoparticles can be composed of different solid lipids, such as waxes, fatty acids, and glycerides, which can be stabilized using various surfactants. Solid lipid nanoparticles have attracted considerable interest from researchers due to their innovative and adaptable properties. Furthermore, this delivery strategy offers many benefits over standard colloidal carriers such as polymeric nanoparticles, emulsions, and liposomes. Solid lipid nanoparticles are one of the technologies developed to address challenges related to drug bioavailability and targeting delivery. In this review paper, we have compiled all the essential information concerning solid lipid nanoparticles, including a general introduction, multiple techniques of preparation, and the numerous excipients related to the formulation. Various features of drug inclusion and manufacturing models, as well as their applications, are thoroughly covered. They can improve pharmacokinetics and modulate drug release. The prospect of surface modification, increased penetration across multiple biological barriers, chemical resistance, and the capacity to encapsulate two or more therapeutic substances simultaneously leads to widespread interest in solid lipid nanoparticles.</p> Graphical Abstract <p>The graphical abstract depicts SLNPs as a versatile DDS, as well as their structural makeup, which includes a solid lipid core supported by surfactants and co-surfactants. It describes many preparation processes, including high-pressure homogenization, microemulsion, and double-emulsion procedures, etc. It focuses on medicinal applications such as topical, oral, and parenteral administration, gene therapy, and cosmetics. The ability of SLNPs to increase bioavailability, improve stability, overcome biological barriers, and facilitate regulated drug release has also been established.</p> <p></p>