Line intensity mapping is an emerging observational technique to measure the large-scale structure of the Universe in three dimensions, traced by a redshifted emission line, without resolving individual objects. Future experiments promise to extend the observable volume beyond the redshift reach of traditional galaxy surveys, improving precision on the LCDM cosmological model and extensions to it. I will discuss the science potential of such experiments, focusing on far-IR lines detectable at millimeter wavelengths. I will then present SuperSpec - a mm-wave spectrometer that performs the spectral separation entirely on a silicon wafer - and our imminent first demonstration at the Large Millimeter Telescope. Finally I will discuss how SuperSpec technology could power future intensity mapping instruments with orders of magnitude more sensitivity.