A new generation of wide-field emission-line surveys based on integral field units (IFU) is allowing us to obtain spatially resolved information of the gas-phase emission in nearby late-type galaxies, based on large samples of HII regions and full two-dimensional coverage. These observations are allowing us to discover and characterise abundance differentials between galactic substructures and new scaling relations with global physical properties. Here I review some highlights of our current studies employing this technique: (1) the case study of NGC 628, the largest galaxy ever sampled with an IFU; (2) a statistical approach to the abundance gradients of spiral galaxies, which indicates a universal radial gradient for oxygen abundance; and (3) the discovery of a new scaling relation of HII regions in spiral galaxies, the local mass-metallicity relation of star-forming galaxies. The observational properties and constrains found in local galaxies using this new technique will allow us to interpret the gas-phase abundance of analogue high-z systems. 1. Introduction The study of the interstellar medium (ISM), like many other areas of astrophysics, has undergone a remarkable acceleration in the flow of data over the last few years. Large surveys such as the 2dFGRS [1], SDSS [2], GEMS [3], or COSMOS [4], to name a few, have revolutionised our understanding of the Universe and its constituents as they have enabled us to study the global properties of a large number of objects, allowing for meaningful statistical analysis to be performed, together with a broad coverage of galaxy subtypes and environmental conditions. The nebular emission arising from extragalactic objects has played an important role in this new understanding. Nebular emission lines have been, historically, the main tool at our disposal for the direct measurement of the gas-phase abundance at discrete spatial positions in low redshift galaxies. They trace the young, massive star component in galaxies, illuminating and ionizing cubic kiloparsec-sized volumes of ISM. Metals are a fundamental parameter for cooling mechanisms in the intergalactic and interstellar medium, star-formation, stellar physics, and planet formation. Measuring the chemical abundance in individual galaxies and galactic substructures, over a wide range of redshifts, is a crucial step to understanding the chemical evolution and nucleosynthesis at different epochs, since the heavy atomic nuclei trace the evolution of past and current stellar generations. This evolution is dictated by a complex array of parameters, including
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