 Here we're zooming into the massive galaxy cluster Able 370, embedded in the middle of a field of 8,000 galaxies flung across space and time. Hubble is mapping regions previously observed by Spitzer. The two telescopes are working together to detect and study some of the universe's earliest galaxies. Spitzer imaged a much larger area of the sky than Hubble, but could not measure the distances to the galaxies it observed. Hubble, in a major survey, is now coming back to the full area of sky covered by Spitzer to measure the distances to thousands of galaxies. Astronomers anticipate that the survey will yield new insights into when the most massive and luminous galaxies formed and how they are linked to dark matter, and how the dynamics of the clusters influence the galaxies in and around them.