Hi guys, Last term I joined the research group of one of the professors in my university, and I did a one-semester research project with him. He offered me to continue on with the project and with his group for my final year thesis, but I think I do not want to. This is because I have decided that I want to do theoretical physics, and I will join one theoretical condensed matter group. So, I want to write him a thank-you email, for all what he has given to me. Do you guys have a sample of thank-you letter, or perhaps, could you give me ideas, tips and hints of writing one?