I've worked for many years trying to connect physical theories to experimental observation 
What inspired me about going into particle physics was at the time it struck me as being the most fundamental where you had a chance of understanding about the laws of nature. The most exciting time has been when the gluon was discovered
When it was discovered at Desi it was certainly a very exciting and rewarding time for me. To see the ideas I had worked on come to fruition
What is amazing is that something as simple and elegant as the standard model can describe all of the forces in nature with the exception of the gravitational interaction
In the late 60s our understanding of the nucleus was based on the idea there must be a strong force to overcome the electric magnetic repulsion of the protons 
But the origin of the strong force was somewhat unclear
I went to the laboratory at CERN in Geneva and there continued the work on field theory descriptions and strong interactions involving quarks. At that time it wasn't commonly accepted that quarks existed and while I was there there was a fundamental discovery of the jeeps I which is the bounce state of the charm anti-charm quark
Which initially people did not understand but subsequently realised that it could only respond to quarks. Gluons are central to our understanding of the strong interactions they are the force carriers analogous to the photon which mediates the electro-magnetic reaction. They couple to quarks and bind them together
What Jon Ellis and Mary Key-Guyard and I did. Was to realise that you could look for the gluon in an analogous way to the way quarks have been looked for by studying the jet of particles that they turn into
So in a process in which you have an electron-positron annihilation into a photon producing a quark antiquark and gluon final state. You would expect to see three jets and there angular distribution would be characteristic of the interaction of the gluon with the quarks. 
This was subsequently looked for at Desi and indeed they found unambiguous evidence that there was a new particle beyond the quarks which had the properties of the gluon
That discovery was really fundamental to our understanding of the strong interactions  
I went from CERN to Caltech having some understanding of this development of the model of QCD for the strong interactions. Surprisingly this was not particularly well studied at the time. 
At lunch I was sitting opposite Feynman. He was talking about his part in the model and I was surprised because at CERN we had learnt that we could calculate what went on inside the so called black box that Feynman had where the partons interact and I said why don't you calculate this and Feynman ignored me completely and carried on talking and I thought well I am just a little person which doesn't matter but he came into my office that afternoon and asked what I meant and I said: "well we have a candidate theory called QCD which is quite promising." And for the next month or two he would come into my office occasionally. What he wanted to do was to discover QCD for himself and he would say what he'd done and I'd say that's how it goes but you've missed something else
So, my work which has largely been looking at supersymetric extensions of the standard model ultimately relates to the nature of unification. Be it grand unification or string unification and one of the active areas that I am involved in is trying to make predictions for the standard model in the context of an underlying unified string theory. 
Why the mathematics that we discovered should be relevant to the physical processes is surprising I think and something that may have a fundamental reason but continually amazes me *laughs*
