Since its construction received lawmakers' approval in 2014, Elon Musk's massive Nevada Gigafactory has been the key to his dream of mass-produced lithium ion batteries. Now the facility has an official opening date.

On July 29, the Gigafactory will hold its grand opening--an invitation-only event open to certain Tesla customers and not, as of yet, to the media, according to Fortune. It's the next step for Tesla in mass producing the batteries its vehicles use, which the company says will help it lower prices and meet current demand.

The event isn't the first time Musk has unveiled something new in a customer-centric fashion. The unveiling of the Model 3, for example, took place in front of a small crowd of 800 people--most of them randomly selected Tesla owners. Gigafactory invitees include customers who had referred five other Tesla customers.

Tesla already offers the cheapest electric car on the market, the $35,000 Model 3, which was unveiled in April and is expected to start shipping next year. Musk's company has received 400,000 preorders and counting. The opening of the gigafactory should help Tesla fulfill those orders and future ones.

Musk has said that when the Gigafactory, which is located in the city of Sparks, is operating at full capacity in 2020, it will produce more lithium ion batteries than the rest of the world combined did in 2013. The company estimates it will employ 6,500 people at its factory by this time.

So far, though, the Gigafactory, which will cost an estimated $5 billion to build, is far behind its projected pace for hiring. The 2014 report that helped Tesla earn a $1.3 billion tax incentive estimated that Tesla would create 700 jobs in Nevada by the end of 2015, but that number turned out to be 272. State officials accounted for the shortfall with the fact that the factory is being built in phases--and said the 2020 estimates still apply.

Though its construction is ongoing, the Gigafactory already produces the Tesla Powerwall and Powerpack batteries used to power homes and industrial buildings.  "Our goal," Musk said at the batteries' 2015 unveiling, "is to fundamentally change the way the world uses energy."

Musk believes it would take about two billion batteries to power the entire world. While that's highly ambitious, he points out that that that level of scaling is achievable--that's how many cars are currently on the world's roads. And factory that can mass produce these batteries is a good and necessary next step to achieving Musk's goal of a world that doesn't rely on natural resources for energy.