This dissertation presents the results from experiments studying the pressure-dependence of properties associated with the glass transition in the glass-forming liquid cumene. Through the use of a diamond anvil cell, we achieve extremely high pressures over 40,000 atmospheres. A new technique is refined to directly measure the glass transition temperature Tg extremely accurately, and we show that thermodynamic scaling is capable of describing the liquid�glass transition boundary up to record-high pressures. Optical techniques are also implemented to probe the system dynamics in the viscous regime leading up to the glass transition. We present laser light-scattering measurements of the dynamic susceptibility spectra, obtained under isothermal conditions at 75 C, from which we measure the system\u27s relaxation time as it slows down with increasing pressure. Through a more in-depth analysis, we determine the crossover density predicted by mode coupling theory, and by combining this with previous measurements, the dynamic crossover boundary is mapped up to record-high pressures for any system. Lastly, another isothermal light-scattering experiment probing the longitudinal and transverse acoustic modes is presented, providing an alternative probe to structural relaxation processes. Through the combination of all of these high-pressure techniques on a single glass-forming system, a much greater understanding of viscous liquids and the glass transition is achieved. Furthermore, the development of these techniques represents a major contribution to the field, allowing other researchers to perform similar high-pressure experiments on other systems
