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Big-bang nucleosynthesis (BBN) describes the production of the lightest elements during the first three minutes of cosmic time, and represents our earliest reliable probe of the universe. BBN has stood as both cornerstone of modern cosmology and particle astrophysics, measuring the cosmic baryon content and probing physics beyond the Standard Model. We will review the status of BBN, emphasizing the transformative influence of cosmic microwave background experiments, particularly Planck, in precisely determining the cosmic baryon density, and the impact of recent nuclear reaction measurements. Standard BBN combines this with the Standard Model of particle physics to make tight predictions for the primordial light element abundances. Deuterium observations match these predictions spectacularly, helium observations are in good agreement, but lithium observations (in metal-poor halo stars) are significantly discrepant-–this is the ”lithium problem.” Going beyond the Standard Model, BBN probes new physics at play when the universe was seconds old, deep into the radiation era. We conclude with a glimpse of prospects for the future.