Tesla CEO Elon Musk is no fan of Facebook and makes no attempts to be polite about it. The social media network and Musk have been critical of one another in the past and the feud continued on as Facebook officials criticized Musk’s understanding of artificial intelligence, causing Musk to strike back.

According to Business Insider who gave the initial report, Facebook’s head of AI threw shade Musk’s way by saying that he didn’t understand AI, to which Musk had a simple response:

And this week, when Facebook’s head of AI, Jerome Pesenti, criticized Musk’s understanding of artificial intelligence — saying on Wednesday that Musk “has no idea what he is talking about when he talks about AI” — Musk took the opportunity to clap back.

“Facebook sucks,” Musk said via Twitter for iPhone at about 1 a.m. PT on Thursday.

Facebook sucks

— Elon Musk (@elonmusk) May 14, 2020

The “AGI” that Pesenti is referring to is the theoretical “Artificial General Intelligence.” AGI is proposed to be a more humanlike machine intelligence that learns and adapts the same way we do. Pesenti noted that AI is nowhere near human intelligence yet.

Musk, however, believes that we’re underestimating AI, as Business Insider reported:

“I think generally people underestimate the capability of AI — they sort of think it’s a smart human,” Musk said at a talk with Alibaba CEO Jack Ma at the World AI Conference in Shanghai, China, last August. “But it’s going to be much more than that. It will be much smarter than the smartest human.”

And he’s made much more alarming statements than that. “AI is a fundamental risk to the existence of human civilization,” he said in 2017. “I have exposure to the most cutting-edge AI, and I think people should be really concerned by it.”

To that end, Musk has another company — Neuralink — that he’s hoping will bridge the gap between human intellect and what he sees as far superior artificial intelligence. He was also an investor in several AI startups.

Facebook AI and Musk’s AI do wholly different things. Facebook uses AI as a way to accomplish a myriad of tasks, including identifying harmful content on the platform and collect information about you in order to serve you to your specific interests. Musk’s AI is learning to navigate and drive vehicles by itself. Musk has stated that his AI is so far ahead of the competitions that it’s like comparing Google to other search engines.