Weak lensing is one of the primary probes of the matter distribution in the Universe and a cornerstone of the Euclid mission. Its cosmological exploitation requires accurate knowledge of the redshift distributions of source galaxies. A major part of this thesis focuses on the calibration of these distributions, including the validation of spectroscopic reference samples and the development of the Multi-Passband Transfer function, a catalogue-level method designed to mitigate biases between spectroscopic reference samples and Euclid photometric observations.

This thesis also investigates the galaxy--halo connection at z<1 through galaxy clustering measurements and halo occupation distribution modelling. By comparing galaxy populations selected by colour and morphology, the results extend studies of the colour--morphology relation beyond the local Universe and provide new constraints on the connection between galaxies and their dark matter haloes.

In parallel, I contributed to the visualisation and communication of the cosmic web and other large scale structures within Euclid, developing new approaches for presenting complex survey data to both scientific and public audiences.