Experiments performed in our lab are a unique combination of ultrafast (femtosecond) and surface selective capabilities. We use nonlinear optical spectroscopies to selectively probe molecules in the very thin interfacial region (~10Å). The second order nonlinear optical process of Second Harmonic Generation (SHG) and Sum Frequency Generation (SFG) are symmetry-forbidden in bulk media, but allowed at interfaces. In our experiments we use femtosecond lasers to perform ultrafast time-resolved measurements. This allows us to observe motions and reactions of molecules at interfaces in real time. Our current time resolution is ~140fs.