The Milky Way is teeming with planets intermediate in mass between Earth and Uranus. Some transit their stars, offering astronomers the opportunity to observe their sizes, masses, orbits, and atmospheres. The measured densities of low-mass planets hint at a rich compositional diversity; I will describe our efforts to further probe some of these planets’ compositions through atmospheric observations. Drawing an example from this diverse population, I will present our recent discovery of GJ1132b, a new Earth-size planet transiting a nearby low-mass M dwarf. It is the first known rocky exoplanet for which atmospheric characterization will be possible, either with existing facilities or with the James Webb Space Telescope (JWST). The Transiting Exoplanet Survey Satellite (TESS), set to launch in 2017, will conduct an all-sky search to discover more nearby small planets amenable to mass and atmospheric measurements; I will share our predictions for the planets TESS will find. I will highlight how exoplanet observations over the next decade can contribute toward the long-term goal of characterizing habitable or inhabited worlds beyond the Solar System.