Structure functions and low x physics

In the framework of conventional Regge theory we present a common description of total photon-proton cross-section and proton structure functions in the region $0\le Q^2\le 5{\mathrm{G}\mathrm{e}\mathrm{V}}^2$. Using it as an initial condition in the perturbative QCD evolution equation, we describe structure functions at any $Q^2$ and $x$ - including the small $x$ region explored at HERA.