Solid lipid nanoparticles (SLNs) have gained momentum over the three decades due to its role in improving bioavailability/ drug stability, controlled and targeted delivery, and as vaccine adjuvants. The excellent biocompatibility of lipid nanoparticles and ease of formulation without using toxic solvents are the main reasons for their popularity over polymeric nanoparticles. The performance of SLNs is further improved by use of modified matrix (using solid lipid + oil) e.g., second generation lipid nanoparticles i.e., nanostructured lipid carriers (NLCs). NLCs offer increased drug loading capacity, modulated release profile and stability. The matrix (both oil and solid lipid) plays very important role in performance of NLC. Ample amount of literature is published on use of solid lipids nanoparticles; however, very limited number of publications as per our information discusses the role of oil and their effects on matrix structure.