Abstract: The WFC3 Infrared Spectroscopic Parallel Survey (WISP) is a large ( 750 orbits) HST program using WFC3 slitless IR spectroscopy to detect thousands of galaxies across a wide redshift range 0.3 < z < 2.3. I will present an overview of recent results on emission line galaxies, including a statistical determination of their dust extinction properties and the discovery of a new population of extremely strong emission-line dwarf galaxies. I will also discuss the stellar population properties of passive galaxies at za^1/41.5 derived from the combination of the WISP IR spectra and broad-band HST optical and Spitzer photometry.