We shall present an overview of our VLT studies of such diverse objects as galactic planetary nebulae and blue compact galaxies. Using the FLAMES Argus integral field spectrograph (IFS) we have mapped the sub-parsec, high metallicity regions embedded in typical planetary nebulae and investigated in detail the occurence of the long-standing 'abundance discrepancy problem' in these objects. This study highlights the type of science obtained with a proper synergy of deep emission line spectroscopy with an 8-m telescope and a new recombination line theory for heavy ions. Using the VIMOS IFS we have also studied a class of low metallicity blue dwarf galaxies that exhibit peculiar chemical composition at <100 pc scales: deep spectral mapping allowed us to investigate the variation of the star formation rate across the targets and the homogeneity of their ionized gas in terms of the helium, oxygen and nitrogen abundance. These two examples demonstrate the superb capabilities of VLT IFS for the study of chemically inhomogeneous nebulae at small and large scales.