Left: t₉₀ as a function of the stellar mass (derived from the spectra). The colours indicate different galaxy environments, quantified by the η estimator. Grey dots correspond to galaxies that do not belong to groups or structures, thus denominated field galaxies. The right panel shows the relative fraction (respecting all galaxies in the same environmental category) of galaxies in different t₉₀ bins. Right: t₉₀ as a function of the mean galaxy metallicity coloured by the environment.