Apple is one of the few major technology companies that hasn’t said it’s jumping into virtual reality. But the company is certainly making some moves that suggest it’s thinking about the emerging technology.

Apple AAPL employees have been visiting the Stanford University Virtual Human Interaction Lab quite often lately, the facility’s director Jeremy Bailsenson told The Wall Street Journal at the CIO Network Conference on Tuesday. However, he told the Journal that they don’t have anything to say when they’re there.

“They come and they don’t say a word,” he said of the Apple employees. “But there’s a data point for you.”

The comment is notable for one, important reason: Apple hadn’t visited Stanford’s lab, which is home to its studies on virtual reality and heavily attended by industry heavyweights, in the last 13 years. Apple has since visited the lab three times in the last three months, according to Bailsenson.

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Virtual reality uses headsets to place people in completely virtual worlds. An offshoot, called augmented reality, places virtual elements over the real world. Many major companies are investing heavily in both technologies.

While it’s not a smoking gun, Apple’s attendance at the Stanford virtual reality lab is just the latest indication that the company is at least thinking about virtual reality. In recent months, the company has published job postings on its website looking for virtual reality and augmented reality experts.

Last year, Apple made a significant push into the virtual reality market by filing for several patents related to the technology. Those patents, which were discovered by Patently Apple, a site that tracks the iPhone maker’s patent applications, are designed to enhance virtual reality headsets.

Apple in May 2015 acquired Metaio, a company that was developing augmented reality tools before it was folded into the Apple’s operation.

For more, read: 3 Signs Apple Has Entered the Twilight Zone of Virtual Reality

Meanwhile, Apple has added some big guns to its staff. In a research note in August, Piper Jaffray analyst Gene Munster said that Apple has built a sizable team of virtual reality experts. Last year, for instance, the company poached Nick Thompson, who previously led the audio team on Microsoft’s HoloLens wearable.

Last month, the Financial Times reported that Apple had also hired Doug Bowman, Ph.D. Bowman is one of the world’s leading minds on virtual and augmented reality. He previously served as professor of computer science at Virginia Tech, according to his resume. He was also the director of the university’s Center for Human-Computer Interaction.

All of that makes Apple’s attendance after a more-than-a-decade-long absence from the Stanford VR facility even more compelling.

Apple, after all, is one of the few major companies that hasn’t committed to investing heavily in virtual reality and augmented reality. Google GOOG has already delivered a headset in its Google Glass that attempts to create an augmented experience in the real world. While that product is currently in development and has since been taken off store shelves, Google has indicated it will be doubling down on virtual and augmented reality in the coming years.

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Facebook FB , meanwhile, made a major investment in 2014 by acquiring Oculus for $2 billion. That company’s virtual reality headset, the Oculus Rift, is slated to finally find its way to users this year.

Even Microsoft MSFT is getting into the mix with its own augmented reality headset, the HoloLens.

Apple, however, is notoriously secretive about its plans and has not made any official indication that virtual or augmented reality is in its sights. However, considering most of the market is moving there and the sheer number of moves Apple has made in that direction in the last year, the writing appears to be on the wall.

It also doesn’t hurt that the worldwide virtual reality market is set to explode in the coming years. In December, research firm TrendForce estimated that the market could grow to $70 billion in annual revenue by 2020, up from $6.7 billion this year. Apple, like the others, may want to see how much of that pie it can eat.

Apple did not respond to a request for comment on Bailsenson’s comments.