Elon Musk and Bill Gates have argued over everything from climate change to the pandemic. Here's how their disagreements started — and everything that's happened since.

• Elon Musk and Bill Gates don't seem to agree on climate change, the pandemic, or space travel.

• They've made public jabs at each other for years in interviews and on social media.

• Gates said Musk "was super mean to me" after he took issue with the Microsoft founder shorting Tesla stock.

Bill Gates and Elon Musk haven't always exactly seen eye-to-eye.

While the Microsoft billionaire and the Tesla titan have never appeared to have a particularly cozy relationship, things have heated up over the past few years as the two have openly sparred about topics as varied as electric vehicles and the pandemic.

The two moguls are among the world's wealthiest people, with Musk at No. 1 and Gates at No. 5, according to Bloomberg data as of early September.

While their public spats may not always be serious, they do appear to fundamentally disagree on how to fight disease; how to address climate change; on whether cryptocurrency is legitimate; and on the importance of space travel.

In fact, new details from Walter Isaacson's forthcoming biography on Musk suggest that their relationship behind closed doors may've been more tense than we would've thought.

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

Things first became tense between Bill Gates and Elon Musk in 2020.

At the time, they were both involved in fighting the coronavirus — Gates pledged hundreds of millions of dollars to fight the virus, while Musk was working to source and produce ventilators.

Musk had also teamed up with the German biotech firm CureVac (in which Gates is an investor) to make a device to aid in vaccine production.

But Musk was also frequently downplaying the severity of the virus and strongly criticizing stay-at-home orders.

He'd promoted the malaria drug hydroxychloroquine as a treatment, falsely said that children are immune to the virus, and suggested that coronavirus-deaths data are "misleading."

Gates took issue with Musk's behavior regarding the virus.

"Elon's positioning is to maintain a high level of outrageous comments ... I hope that he doesn't confuse areas he's not involved in too much," Gates said on CNBC's "Squawk Box" in 2020.

The comments struck a nerve with Musk, who taunted Gates on Twitter.

Musk jokingly posted multiple tweets about Gates, writing "Billy G is not my lover" and "The rumor that Bill Gates & I are lovers is completely untrue."

In fact, Musk defended his role in the coronavirus relief efforts.

"Gates said something about me not knowing what I was doing," Musk told The New York Times during a podcast interview in September 2020. "It's like, 'Hey, knucklehead, we actually make the vaccine machines for CureVac, that company you're invested in.'"

But another major source of tension between Gates and Musk appears to be climate change — specifically, how big of an impact Tesla has in reducing emissions and helping the planet.

During a 2020 interview with the YouTuber Marques Brownlee, Gates said that while Tesla had helped to drive innovation and adoption of electric vehicles, he'd purchased different electric car, a Porsche Taycan.

Gates' comments didn't seem to have bothered Musk.

At the time, Musk tweeted that his conversations with Gates had always been "underwhelming."

Musk also took issue with a blog post Gates wrote that questioned whether it was practical to make vehicles like 18-wheelers fully electric.

Though Gates didn't mention Tesla in the blog post, the company has developed a semi, and when a Twitter user asked Musk about his opinion of Gates' comments, Musk replied, "he has no clue."

Gates has issued Musk a few rare compliments over the years.