At the Fox News Republican presidential debate on Thursday, Donald Trump suggested that he has a large penis.

This actually happened.

During an exchange about the personal attacks Rubio has made on Trump, Rubio said that if any candidate "deserved" to be personally attacked it was Trump, because of how much he attacks others.

Trump responded with surprise that Rubio "hit my hands. Nobody has ever hit my hands. I've never heard of this."

Then he spread his palms out.

"Look at those hands. Are they small hands? And he referred to my hands — if they're small, something else must be small. I guarantee you there's no problem, I guarantee."

They later further traded insults, with Trump referring to "little Marco" and Rubio referring to "big Donald."

Just in case you're left in the dark about why Trump might get so worked up about the size of his hands, Vox's Libby Nelson helpfully explains Trump's rich history with the topic.

Why did this even come up? Yes, Rubio made fun of Trump on the campaign trail for having small hands. But it wasn't the first time that's happened.

Trump has famously been defensive of his hands since Spy magazine first called him a "short-fingered Vulgarian" in 1988. Trump still occasionally sends the editor of the now-defunct publication pictures of his hands to prove that his fingers aren't short.