Here you are not looking at a flower, a heart viewed through a scanner or even a work by a contemporary artist but instead at one of the very first galaxies to exist in the Universe. It is not a photograph either - it is a model developed by researchers at the Lyon Centre for Astrophysics Research (CRAL).

Galaxies are above all systems of stars, gas and dust; "islands" in a near-empty Universe which are linked by filaments of matter. Researchers attempt to understand their structure by observing the light emitted by their stars but observation is not the only way of studying them. The images shown here do not come from telescopes but from digital simulation or computer modelling aimed at reproducing the way in which these galaxies were formed. The calculations required to model this process require the simultaneous integration of millions of parameters so the calculations can take a very long time and can only be carried out using supercomputers. The images produced serve to visualize (in artificial colours) the different physical proprieties of galaxies such as the temperature or density of gas.

These images are notably used by scientists attempting to answer questions about the formation of the first galaxies. They have helped in the development of the following scenario - thanks to gravity, matter tends to gather together in zones with the highest density which are linked by filaments of matter to form a kind of "cosmic spider's web". At points where the filaments cross, matter is sufficiently concentrated for the first stars and then galaxies to form.

Thanks to Maxime Trebitsch for his contribution.