Lagrangian Neural Networks
On a personal note, I consider the university class where I learned about Lagrangians for the first time to be a pivotal moment in my life. It was the first time I experienced a fundamental sense of awe and beauty about a mathematical construct, in physics or otherwise. I'd thought physics was useful and interesting before that, but seeing derivation of and application the Lagrangian formulation to mechanical systems was, and is, simply gorgeous to me. And as someone who recently began dipping their toe into neural networks, this is really very cool.