•D:  Crucial.  Strong dependence on baryon density.  Measured from interstellar absorption in UV/Far-UV with HST and FUSE.  Older values are [D/H] = 1.5 +/- 0.2 x 10-5, but we will have an update based on FUSE results on high-order Lyman lines by a volunteer.  Keep in mind that stars destroy D, so these numbers are lower limits.  Can also look in the IGM using high-z quasars.