Now that the centennial anniversary of the first report on pressure denaturation of proteins by Nobel Laureate P. W. Bridgman can be celebrated, this Review on the application of high pressure as a key variable for studying the energetics and interactions of proteins appears. We demonstrate that combined temperature-pressure-dependent studies help delineate the free-energy landscape of proteins and elucidate which features are essential in determining their stability. Pressure perturbation also serves as an important tool to explore fluctuations in proteins and reveal their conformational substates. From shaping the free-energy landscape of proteins themselves to that of their interactions, conformational fluctuations not only dictate a plethora of biological processes, but are also implicated in a number of debilitating diseases. Finally, the advantages of using pressure to explore biomolecular assemblies and modulate enzymatic reactions are discussed.