Unveiling the nature of the "Green Pea" galaxies
We review recent results on the oxygen and nitrogen chemical abundances in extremely compact, low-mass starburst galaxies at redshifts between 0.1-0.3 recently named to as "Green Pea" galaxies. These galaxies are genuine metal-poor galaxies ($\sim$ one fifth solar) with N/O ratios unusually high for galaxies of the same metallicity. In combination with their known general properties, i.e., size, stellar mass and star-formation rate, these findings suggest that these objects could be experiencing a short and extreme phase in their evolution. The possible action of both recent and massive inflow of gas, as well as stellar feedback mechanisms are discussed here as main drivers of the starburst activity and their oxygen and nitrogen abundances.