Star forming galaxies may contain many sources of ionizing radiation, including an AGN, shocks driven by galactic-scale outflows or mergers, star formation, old stellar populations, and ionizing radiation that has escaped HII regions. Distinguishing the main power sources in star forming galaxies remains a complex task. Fortunately, wide integral field spectroscopy with high spectral resolution is able to distinguish among the different power sources by using a combination of spatial information, kinematic information, and emission-line ratios. The combination of integral field spectroscopy and new shock, photoionization and AGN models allow one to separate power sources within galaxies across the full wavelength range from the UV through to the far-infrared. I will present new UV, optical and IR diagnostics for separating power sources and show how wide integral field spectroscopy can be applied to discriminate power sources across galaxies.