Our mission is to study the fundamental interaction of very short, intense pulses of light with matter. The tabletop titanium:sapphire laser system in our lab is capable of generating field strengths in excess of one atomic unit of intensity (3.5×10¹⁶ W/cm²). An equivalent peak intensity could be reached by focusing all of the sunlight incident on the earth to a spot the size of a quarter! At these intensities, Einstein’s description of the photoelectric effect must be completely turned around, as even weak red photons are capable of liberating the most tightly bound electrons in atomic systems. This is accomplished through the absorption of multiple photons through so-called virtual levels. In this new regime, many unusual phenomena are observed, including non-sequential double ionization (NSDI), high harmonic generation (HHG), laser-driven fusion of atomic clusters and even pair production. An understanding of the single-atom response is essential to the study of these processes. We seek to probe the limits of the classical description and to investigate the onset of truly quantum behavior.