Now, scientists using the XMM-Newton, ESA's super-sensitive detector, have begun to pick up some of that missing mass by studying X-ray emissions coming from tendrils of gas stretching between two galaxy clusters, Abell 222 and Abell 223. These gaseous filaments connect many other galaxies in the universe, forming a kind of cosmic web, and studying those other links will be the next task. "This is only the beginning. To understand the distribution of the matter within the cosmic web, we have to see more systems like this one," says astronomer Norbert Werner. "And ultimately launch a dedicated space observatory to observe the cosmic web with a much higher sensitivity than possible with current missions."