Elon Musk called Bill Gates a 'knucklehead' for criticizing his coronavirus response. Here's where their simmering feud began and how it's escalated amid the pandemic.

Elon Musk, left, and Bill Gates.Susan Walsh/AP; Mike Cohen/Getty Images for The New York Times

• Elon Musk and Bill Gates have been feuding over everything from the coronavirus to electric vehicles.
• The two moguls don't see eye-to-eye on electric car technology. Musk has said Gates doesn't know what he's talking about, and Gates has revealed he bought a Porsche electric car over a Tesla.
• Most recently, Gates and Musk have feuded over the coronavirus. Gates called Musk's comments on the outbreak "outrageous," and Musk recently described Gates as a "knucklehead."

Bill Gates and Elon Musk don't exactly see eye-to-eye.

While the Microsoft billionaire and the Tesla and SpaceX titan have never had a particularly cozy relationship, things have heated up over the last six months as the two have openly sparred about everything from electric vehicles to the coronavirus.

The two moguls are currently among the world's wealthiest, eclipsed only by Amazon CEO Jeff Bezos. While their public spats may not always be serious, they do appear to fundamentally disagree about the coronavirus — and as two major players in the treatment of the virus and an eventual vaccine to protect against it, their public clashes carry even more weight.

Here's where the friction between Gates and Musk began and everything that's happened since.