At present there is no correct theory of evolution of F₂(x,Q²) at small x. It is a mixture of hard and soft pomeron exchange and perturbative QCD very successfully describes the evolution of the hard-pomeron component. This allows the gluon density to be calculated. It is somewhat different from what is conventionally supposed, but it leads to a clean PQCD description of the data for the charm structure function. Perturbative QCD breaks down for the evolution of the soft-pomeron component of F₂(x,Q²).

PACS numbers: 13.60.Hb, 12.38.--t, 12.40.Nn