Bi-dimensional self-organising map of the COSMOS2015 catalogue (the two folded dimensions have generic labels D₁ and D₂). In the left panel, only robust spectroscopic objects (CL > 95%) are shown. In the right panel, the SOM is filled with photometric objects (stars and z_phot> 2.5 galaxies). In both cases, each cell of the map is colour-coded according to the median redshift of the objects inside the cell (empty cells are grey, cells filled by stars are black).