Under the auspices of NATO STO AVT-240: Hypersonic Boundary-Layer Transition Prediction, this paper describes the results of close collaborations among the authors toward the fundamental understanding and modeling of the instabilities associated with three-dimensional boundary layers in hypersonic flight. Specifically, the focus is directed towards the crossflow instability. A common geometry is analyzed from both a computational and experimental perspective using methods that are unique to each facility and methodology. Disturbance wavelength and trajectory, surface roughness, and the use of quiet wind tunnels are just a few items found to be key factors in the investigation of the crossflow instability. Quiet tunnels allow experiments to be performed in a disturbance environment comparable to that expected from flight, and the combination of different facilities and computations display a comprehensive analysis that would be unobtainable from any individual approach alone.