What do we really know about the proton?

The proton is a particle which is all around and in us and has been studied in detail for many decades. But what do we really know about it? When the structure of the proton is discussed, do we really discuss the proton or QCD? Has the rise of the gluon distribution as observed at the ep collider HERA for high four-momentum-transfers, Q2, anything to do with the proton? And what happens at Q2 of about 1 GeV2 and below when perturbative QCD cannot be applicable? Can the proton spin puzzle really be solved? What is the "true" size of the proton and what is its shape? All these questions are discussed and some answers are offered.