Hello, Blaine! I'm glad you're not waiting for retirement. I believe that category theory "rewired my brain", changing how I think about everything, and I find that the more math people learn _without_ getting into category theory, the harder they find it to learn. Young students seem to take to it quite naturally.

What sort of problems in crystallography are you working on now? I had a minor flirtation with crystallography, but it was of a very mathematical and useless sort:

* [Diamonds and triamonds](https://johncarlosbaez.wordpress.com/2016/04/11/diamonds-and-triamonds/).