The recent studies of the pressure effects on the intramicellar physicochemical properties of surfactant aggregates using spectroscopic probe techniques are described. This article includes the discussion of the micelle formation under pressure, the intramicellar polarity at high pressure, and the intramicellar viscosity at high pressure. The externally applied pressure serves as an effective perturbation to deduce the interior properties of micellar systems. It is demonstrated that especially for the purpose of this investigation, the spectroscopic probe technique is the most useful methodology if a well-defined probe molecule is employed and if the effect of micellar structure on probe solubilization is negligible. Special emphasis has been placed on the validity of using the intramolecular excimer forming probe,1,3-di(1-pyrenyl)propane (DPP), to determine the pressure effect on the intramicellar viscosity.