Computer simulation of a portion of the Universe, modelling the distribution of 10,000 galaxies in a cube with sides of about 80 Megaparsec. Astronomical observations show that on this scale galaxies do not fill the space in a random way but tend to be clustered, either in filaments, walls or in massive nodes, leaving large voids where the density is virtually zero. This sponge-like structure is here simulated using a particular geometrical pattern called the Voronoi tessellation. The galaxies are colour-coded according to their position: white dots represent galaxies in voids, blue in filaments, green in walls and red in nodes.