Virtual particles cannot become real particles in quantum physics as it is conceived in the current Standard Model of particle physics. There is some fancy math associated with this idea. But that same fancy math dictates that fundamental particles are to be treated as ideal points, which is to say that if there is any internal structure lower than quarks, no one knows or cares about them. Instrumentation capable of energies sufficiently high to break them apart almost certainly exists. The Law of Conservation of Energy demands that even something with an inertial mass as low as that of a neutrino can be converted into pure energy. One of the means for doing this is an appropriate arrangement of a neutrino with its anti-particle. This would yield a pair of infrared photons. So, if a neutrino - antineutrino pair can be annhilated into photons, how does one build a neutrino or an anti-neutrino out of photons? A good friend who happens to be a neutrino physicist tells me this would break a dozen conservation laws ingrained in the Standard Model. Something about his statement still bothers me. Until someone can take neutrinos apart, as far as I am concerned, we don't really know all there is to know about particle physics. The smallest mass / energy particle has to be the smallest fundamental particle, doesn't it?