Using mathematical models, astronomers can remove the foreground light from galaxies within a galaxy cluster. By removing the large-scale foreground light, astronomers are able to identify small-scale structures of background, faint, lensed galaxies. Shown here is galaxy cluster Abell 2744 before foreground light subtraction (left) and after foreground light subtraction (right). Multiple distant, faint galaxies become visible using this technique. Those in the circles are background galaxies that are possibly very distant, i.e., those with possibly very high redshifts. Credit: Livermore, Finkelstein, & Lotz 2016