First, it was to explain all the different ways you can manufacture microfluidic chips. That is exactly in my realm of knowledge, and it made me very happy that I could give a helpful, high-level, general overview of the field to a student completely new to the concepts.
Second, it was to share my technical knowledge on thermal control systems. I have built two machines with thermal control systems, and previous students in my lab have built three or four more machines with thermal systems. The student needing help has no fabrication experience, control systems knowledge, or hands-on feel for how to build equipment. I showed them my lab, my current equipment, and the old unused equipment. Between all the examples, I think I was able to show several ways of designing a solution to the problem he was working on.
Third, it was to present on how to design a good case study, and find speakers, and put together a panel for a conference. This is in relation to the conference I helped organize this past Spring Break, which I will be doing again this year.
Fourth, it was my knowledge on life in grad school. I organized the Orientation activities for the new MechE grad students this year, and I got lots of questions. From the logistics of classes and paperwork, to getting around campus, to the expectations in grad school and navigating the tricky lab/advisor relationships - I fielded as much as I could, and knew where to point people when I didn't know the answer. Even after Orientation, there have been lots of new students in my office, and it's been a pleasure to welcome them to the group, and be available for those random questions that pop up, and help them settle in to graduate life if they need it.
When I sat down to think about all this, I was struck by how far I've come. This is my fourth year in grad school. If this was undergrad, I would be a senior. I am supposed to know my stuff by now. And finally, I feel like I do actually know what I'm talking about. That's not to say I know everything or have nothing left to learn - far from it. But I can contribute a) high-level knowledge of my field, b) detailed technical expertise, c) committee organization and conference pointers, and d) general graduate school advice. I'm not sure what other categories there are left!
So can I graduate yet? :)