Second Year Student. What should I do?

I am a second year undergraduate student studying physics. I have been feeling a calling to go towards fusion since I want my children’s children to see the beautiful world around them.

I have an opportunity to pick up more credits, whether that be a minor and graduate on time, or another major and graduate late.

I plan on going to graduate school, but if I want to pursue this field of study, how should I narrow down my physics studies, and what kind of minor would be helpful for my employment/future research opportunities.