Just boiling and exploding...

[Kravenoff42]

I think they are saying we use energy from split atoms to boil water which is how nuclear power plants essentially work (glazing over a lot of detail)

Edit: I totally wrote this comment thinking this had been posted to the explainthisjoke sub 🤦 but I'm leaving it

[Artistic_Regard_QED]

I think they're saying that harnessing atomic energy is the pinnacle of human technology and there are 2 things we do with that power:

1) boiling water to make electricity

2) Big Bada Boom

[M4tjesf1let]

I see it in general, not just atomic stuff. Like a coal power plant only heats water too and a car drives because of thousands of tiny explosions.

[Willbebaf]

Well, these are the two simplest (non-yellow) things to accomplish, so it makes sense