Robert Pettitt, via twitter asked:
Can you see or accurately visualise sub atomic particles or are they known only by maths and/or inference?
Martin - You can see a nucleus and the nucleus of a hydrogen atom is a proton which is the same. You can't see below that at least with a source of neutrons that ISIS produce, but you can see down to the level of the proton.
Using scattering techniques you can image inside the nucleus and distinguish three groups of charge, i.e. the quarks. Pmb, Wed, 5th Dec 2012