Early-type galaxies are now known to also contain a rich and complex interstellar medium. I will discuss how with SAURON integral-field observations we can understand what powers the nebular emission that most often gives away the presence of such a medium. In particular, I will show that central AGNs can only ionize the gas in the central regions of early-type galaxies, a finding that has strong repercussions for our understanding of AGN activity in large spectroscopic samples such as provided by the Sloan Digital Sky Survey.