Time has come for me to do my master thesis project, and Photon-Photon scattering is a hot candidate! Right now I'm just trying to get into the subject, and would be really happy if someone who knows about this could help me. I am familiar with basic quantum mechanics, and am right now studying QED and quantum optics, but any help on any level would be great! I would also really appreciate some good links/references about Photon-Photon scattering in general, and the following subjects in particular: *The Heisenberg-Euler Lagrangian, and the resulting nonlinear corrections to Maxwell's vacuum equations. *Suggested Photon-Photon scattering detectors. *High intensity lasers in general. *Ultra-short intense lasers (chirped pulse amplification). *Free electron laser (FEL).