Four galaxy clusters embedded in the cosmic web, the wispy network of both dark and baryonic matter that is believed to pervade the Universe. This image was extracted from a numerical simulation of the formation and evolution of cosmic structure.

Four very massive galaxy clusters are visible where the concentration of galaxies (shown in white and purple) is higher. Two of the clusters, in the lower left corner of the image, are in the early phases of a merging process; the other two clusters can be seen in the central part of the image, just above the centre. The filamentary structure formed by the four clusters extends toward the right side of the image, where several less massive systems can be seen.

Galaxy clusters form in the densest knots of the cosmic web, where filaments intersect. The density of gas in the filaments that link the clusters is represented with different colours, with dark brown indicating less dense regions and brighter colours (from orange to yellow and green) indicating increasingly denser regions.

The image shows a portion of the cosmic web that spans about 260 million light-years across.