Early seminal work in action-based experiments by Marcus demonstrated the acquisition of transient and two-dimensional electronic spectra of Rb vapor by monitoring modulations in the fluorescence signal as a function of the pulse delay times. More recently, Brixner reported 2D electronic action spectra of neutral species in the gas phase generated in molecular beams and detected with mass spectrometry via photoionization. Stienkemeier has likewise measured 2D electronic action spectra via photoionization of neutral gas-phase species using He nanodroplet techniques. In related studies, Allison has directly measured electronic transient absorption spectra of neutrals produced in molecular beams using cavity enhancement and frequency-comb laser sources. Collectively, this impressive growing volume of studies are opening new avenues for unraveling fundamental molecular interactions and dynamics.