Twinning in crystals is when two (or more) lattice intertwine, sharing some lattice points in a particular way. I'm working on a essay, due to the editor on Monday. I've researched and wrestled with the topic. I've shuffled index cards around and outlined and sketched and written. And today, with all the tough parts written and the rest quite nicely sketched in, I realized that this was a twinned essay.
Tomorrow is now devoted to some very careful surgery to separate the two pieces so they can each stand on their own. Good news is that they will both find a home this summer.