Hi, I'm beginning Physics graduate school this Fall. I have an undergrad in EE, and I have interests in various areas. I intend to make up my mind about the exact field of Physics I would like to specialize in, by the end of my first year in grad school. I have a few questions about how the Physics grad school and postdoc system works in the US. Perhaps some of my questions are immature and/or ill-posed. I have some ideas of my own, but I don't know exactly how the system works, and I would appreciate replies from people who're experienced about it. 1. Is research work in field X ever considered a deterrent if one switches to field Y during grad school (X, Y are two distinct sub-disciplines in Physics)? 2. Is it common to switch areas after a PhD, i.e. when one is getting into a post doc? 3. Is it possible to switch from theory to experiment or vice versa at the time of a post doc? I understand that there's a big theory-vs-experiment divide in academia/outside , but are there still opportunities for people who like both equally (the last time I raised this question in a different context on this forum, I was told that it is silly and unthinkable to 'like' both, but I'm sure there are people -- however small in number -- who would think like me?). I will probably have more questions, based on the responses I get. Thanks for your time!