Nowadays solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) have been investigated as carrier systems for many applications. SLNs consist of pure solid lipids, while NLCs are made of a solid matrix that entraps liquid lipid nano-compartments. These systems revealed several advantages compared to other colloidal carrier systems. They provide a controlled drug release and an increase in chemical stability of the incorporated drugs. Moreover, they are safe carriers which can be produced easily in a large scale. This paper reviews the commonly used materials, production techniques, characterization, and physical stability of these systems.