1. Feynman says all of electromagnetism follows from Maxwell equations. 2. Somebody (Pointing to a Feynman diagram of a photon/electron reaction) said all of electromagnetism is in that one diagram. So, can anyone help me with these two questions: how does point 1 come from point 2. And, how does a photon come from an EM field just by using it in a Langragian form?