Aurora Innovation, the autonomous tech startup run by the former head of Google’s self-driving car division, just landed a funding round of half a billion dollars from a large group of investors — and Amazon was one of them.

It’s the latest sign that the online retail giant is pushing hard into the world of autonomy. Late last month, CNBC discovered that self-driving truck startup Embark has been hauling Amazon cargo on some of its test runs. One week before that, Amazon announced it had developed a small autonomous delivery robot named Scout.

“We are always innovating and working with innovative companies to improve the customer experience and safety of our team,” a spokesperson for Amazon said last week in response to the Embark news. “We think successful over the road autonomy will create safer roadways and a better work environment for drivers on long-haul runs.”

Amazon has poked at a number of different sections of the automotive industry, too. It released a dashboard product with Alexa, and has integrated the voice assistant into a number of cars. The company also announced a service last year where it will allow people to accept deliveries in the trunk of their car.

Amazon’s autonomy ambitions are not exactly new; the company has been working on drones for years, and is rumored to be developing a home robot. But the investment in Aurora is the first public connection between the company and self-driving passenger cars.

Neither company disclosed how much of the $530 million funding round was contributed by Amazon. (Aurora has now raised $620 million to date.) Sequoia Capital and a number of other investment firms were also involved in the funding round.

“Amazon’s unique expertise, capabilities, and perspectives will be valuable for us as we drive towards our mission,” Aurora wrote in a blog post about the news.

Aurora was started in 2016 by Chris Urmson shortly after he left his post atop Google’s self-driving car program. (He left just a few months before that program was spun out as Waymo.) Urmson quickly recruited Sterling Anderson, who ran Tesla’s Autopilot team, and former Uber autonomy head Drew Bagnell. Anderson and Urmson were sued by Tesla for allegedly poaching employees to start Aurora, though the lawsuit was eventually settled.

The company has worked quietly since then on a software stack for self-driving cars. Essentially, Aurora wants to make the nervous system for autonomous vehicles, and then partner with automakers to put that software into their cars. Aurora announced at the beginning of 2018 that its first customers will be Volkswagen and Hyundai, and a few months later added EV startup Byton to that list.

While there are dozens of companies working on self-driving technology, including most of the traditional automakers themselves, Aurora is often singled out for the team it has built. “[W]e met with nearly every AV company in the world from Detroit to Singapore. But each discussion brought us back to Chris and his team as the benchmark against which everyone else was measured,” Carl Eschenbach, a partner at Sequoia, wrote in a blog post.

In an interview with The Verge last year, Anderson put it more succinctly. “As the saying goes, A players want to work with A players,” he said. “I think the very common response from those who come onsite to interview at Aurora is ‘holy shit, you have an impressive team.’”

Update February 7th, 2:19PM ET: Added comment from Amazon.