Ionic liquids (ILs) have shown immense potential as suitable alternatives to environmentally damaging volatile organic solvents (VOS). These unique materials possess very unusual physicochemical properties, such as low melting point, high boiling point, excellent thermal and chemical stability, large electrochemical window, very low volatility and high conductivity. One of the most important features associated with ILs is that their physicochemical properties, like viscosity, density, hydrophobicity, solubility, polarity, etc., can be effectively tuned for desired applications just by tuning the structures of cations and/or anions. Further, these designer solvents show dual behavior, i.e., electrolytes and solvents. In the last two decades, these unique materials have shown tremendous application potential in various interdisciplinary research areas, such as synthesis, catalysis, separation, extraction, nanoscience, and pharmaceutics, among many others. Further, the formation of surfactant self-assembled nanostructures (micelles and microemulsions (ME)) within ionic liquid-based systems of immense importance due to the vast utility of these nanostructures well as ILs in various fields of science and technology. These microheterogeneous systems can be effectively used as greener alternatives to those environmentally harmful volatile organic solvents which are largely used for academic and industrial research purposes.atile organic solvents which are largely used for academic and industrial research purposes. The IL-based self-assembled nanostructures show major advantages due to their affinity to solubilize many chemical and biochemical solutes (both hydrophilic as well as hydrophobic), thereby expanding their potential application as solubilizing media, media for synthesis, catalysis and biocatalysis, separation and extraction, drug delivery vehicles, and media for biochemical stability (e.g., protein and enzyme stability). This book chapter will highlight the formation and utility of various types of self-assembled nanostructures formed by surfactants, polymers, etc., within Ils-based media.