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Published online by Cambridge University Press: 22 July 2013
In spite of extensive research over the past decades, a complete physical picture of theorigin of the prompt gamma-ray burst emission is still lacking. During recent years,evidence has been accumulating that the jet photosphere plays an important role. In thispaper we summarize the lessons learned from Fermi observations regardingthe behavior of the photosphere and discuss why photospheric emission does not necessarilyappear as blackbody radiation. We concentrate on two strong and important bursts, GRB090902B and GRB 110721A, which serve as examples of the standard appearance photosphericemission may have in gamma-ray burst spectra.