In ecology we refer to people by the topics they study. For example, you can be a "plant person", an "elephant person", a "fish person", etc. Generally we use it to refer to the primary organism we study but sometimes we like to say "that guy, he's a molecular-microbial person" which tells us that he likes really small complicated things. Essentially, it's a shorthand way of letting people know what you study without spewing your dissertation all over them. Really, it's just a quick way to say, "I'm a nerd and I'm OK with that."
I find this way of pegging people both charming and a bit daunting. When I first met many of the students in my cohort they already knew what kind of "person" they were but I didn't. It set me on edge as I fluctuated between being a "crayfish/invert(ebrate) person" to being a "plant person." I'm really not ready for my title. I'm an undecided person. Undecided, but looking forward to specializing. It seems to me that being an expert in a topic carries a great deal of responsibility, but I look forward to to the day when I can stop saying "I don't know." And as I write that, I realize it will be a very sad day when I know everything. If I am going to be an ecologist, a teacher, a crafter, a person, I need to value asking a question and seeking the answer. It's only partly about the end result, but what I do while I get there.