Last week, we published a paper, led by Arpan Das at the Scuola Normale Superiore in Pisa, Italy, on high mass X-ray binaries and their impact on the 21-cm signal during cosmic reionization. Here we used the “Birth of a Galaxy” simulations to calculate how the host galaxy attenuates UV and X-ray radiation from these objects. This effect is important in determining the exact imprint these high-energy photons have on the surrounding intergalactic medium, heating and partially ionizing it in the process, which will be detectable with future 21-cm experiments, such as SKA and HERA. Image credit: ESO.