Tunneling spectroscopy has been central to our understanding of many electronic systems; for example, features in tunneling spectra arising from electron–phonon coupling were key to confirming the BCS description of conventional superconductivity. However, in many strongly correlated two-dimensional electron systems, conventional tunneling measurements are often either not feasible or are easily distorted. I will describe a time-domain tunneling technique that uses millions of short voltage pulses and measurements of the resulting charge response to construct precise tunneling spectra, even in electrically insulating phases. Applied to 2D electron systems, this method yields the single-particle spectral function, providing access to the energies, momenta, and lifetimes of electronic states. Using this approach, we have discovered a novel spectral feature that reflects the vibrational modes of an electronic Wigner crystal and have determined the spin polarization of the strongly correlated 2D electron system.