Diffractive phenomena observed at HERA are starting to give us a new perspective on the deep inelastic scattering. In this talk the properties of diffractive events observed by the H1 and ZEUS experiments are described. We give also a theoretical interpretation of the diffractive results with special emphasis on the phenomena at the boundary of soft and hard physics. In this region perturbative QCD seems to provide a useful guide. Simple models can be constructed which allow to connect the photoproduction, deep inelastic scattering and diffractive phenomena in a quantitative way.