PARTON DISTRIBUTIONS OF REAL AND VIRTUAL PHOTONS Torbjorn Sjostrand, John K Storrow and Andreas Vogt Recent progress on the parton distribution functions of the photon, both real and virtual, is briefly reviewed and experimental possibilities at HERA are discussed. LU TP 96-5 and MC-TH-96/04, January 1996, to appear in the proceedings of the Durham Workshop on HERA Physics, ``Proton, Photon and Pomeron Structure'', 17--23 September 1995, Durham, U.K.