In case it's not clear, the question in the title is figurative. If you stole something from a former lab, you don't need to air that here. But I am curious this morning, if people can pin down what the most critical thing they have learned from their various mentors is. For me, it would be something like:
Undergrad mentor: There's few people I know who have more love for what they do. Anytime I hear UGM described by others, the word "passion" gets thrown around a lot. The most important thing I learned from this person was to do what you love.
Grad mentor: GM taught me how to be a scientist. I went to work with GM because of what they do, but came away from that lab knowing what it meant to be a scientist. This isn't as common as we would all like to believe.
Postdoc mentor: I learned to write as a postdoc. That's not to say I was a bad writer prior, but I learned to write in my postdoc lab. I gained a lot of skills and depth there but learning how to be a successful communicator has been the most critical skill I left with.
How about you?