2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/4730In this brief contribution, I touch on a subset of recent efforts in spectral and opacity modeling aimed at improving our understanding of brown dwarfs, L dwarfs, and T dwarfs. I discuss theoretical calculations of the alkali line profiles, newly generated CrH opacities, new evidence for refractory rainout in T dwarfs from optical spectral measurements, and the distinction between brown dwarfs and planets.9 pages, in newpasp.sty format, 4 figures. To be published in the Proceedings of IAU Symposium 211 entitled {\it Brown Dwarfs}Astrophysicstext