Some of the greatest mysteries remaining in cosmology concern the growth of structure during the cosmic “dark ages” between the last scattering of the cosmic microwave background and the galaxy-dominated era we live in.  Soon a new set of low-frequency radio telescopes will begin probing this era by studying the redshifted hyperfine transition of neutral hydrogen in the intergalactic medium.  I will describe what we hope to learn about the dark ages, the first galaxies, and cosmic “reionization” from these observations, as well as the unique challenges posed by the measurements.