One of the most important open issues in astronomy is the assembly of galactic disks. I approach this subject from an observational perspective, tracing the kinematic evolution of star-forming galaxies since a redshift of 1, or over the last 8 billion years of the universe. I will discuss recent results that show the progressive (and mass-dependent) assembly of disk galaxies over this time period. I will also introduce a mass threshold, below which disk formation is not guaranteed in today's universe. These results strongly challenge the traditional analytic model of galaxy formation and provide an important benchmark for simulations.