The brane-antibrane annihilation at the end of brane inflation creates mostly massive closed strings. But standard BBN requires mostly open strings (photons, electrons and neutrinos). So the question is whether these closed string degrees of freedom can get successfully transformed into the required open strings, with negligible graviton production and non-lethal amount of thermal relics. In this talk, we will examine the thermal history after the brane inflation, and explain how the properties of the warped compactification nicely solves this reheating problem. We also discuss the hidden dark matter candidates naturally arise in this study, and their novel implications to the dark matter coincidence problem and the ultra high energy cosmic rays.