Grandma: (to Grandpa) Good thing we had your nitro with us today!

Chantelle: His nitro? What's that?

Grandma: When he gets chest pain he's supposed to spray it, and if he has to spray it twice we take him to the hospital. I don't remember the full name. I think it's nitroglycerin. 

Chantelle: Grandma, I'm pretty sure nitroglycerin is dynamite...

Grandpa: Well I guess instead of blowing up my heart, maybe we can blow off my head.

And then I discovered that we were both right. Nitroglycerin is used both to make dynamite AND to treat heart problems...

Awesome.