It’s Christmas 2016—prime gift-giving season. As many in the retail industry predicted, millions of people are unwrapping a Vive, Rift, PlayStation VR, or some other virtual reality device. I imagine many people, when faced with this unusual contraption, responded as my grandfather did when I gave him his first experience of virtual reality in 2014: “What am I supposed to do with this?”

Then they did what we all do nowadays when we have a question—they asked Google. According to Google Trends, the use of the search term “VR Content” tripled between December 23 and December 26, 2016. Not coincidentally, so did queries for “VR Porn.” It seems people received their VR goggles, tried out a few stock demos, and then sought out, well, porn.

In the late ’90s, before I founded Stanford’s Virtual Human Interaction Lab, my initial research wasn’t geared toward VR as a consumer product. I worked in a psychology department at UCSB, and we viewed VR as a tool to understand basic brain science, not a gadget that sits next to the TV set. In fact, in my lab at UCSB we likened the VR system to a functional Magnetic Resonance Imaging machine—a ridiculously expensive, bulky technology that needed constant maintenance and could only be administered by trained experts.

When I arrived at Stanford, I switched from a psychology department to a communication department studying media use. As my thinking evolved I began to imagine a world in which avatars and virtual reality were everywhere. I imagined a future as William Gibson or Neal Stephenson described it—with VR everywhere. And that raised a host of fascinating, sometimes troubling questions. Could politicians use avatars to rig elections? Could VR make advertisements more persuasive? Could changes in the weight of your avatar change the way you eat in the real world? But even as I explored these knotty issues, I was able to sleep at night just fine. After all, the technology was still confined to those with six-figure budgets and the engineers necessary to keep the systems running.

But in 2010 my thinking began to change. Maybe it was that I was starting a family (my first child was born in 2011) or that I was witnessing the first wave of consumer VR technology flourish when Microsoft created the Kinect. Perhaps I was influenced by new mentors, people like Jaron Lanier—whose vision of VR was synonymous with a hippie-inspired notion of self-transformation—and Philip Rosedale, whose unbridled enthusiasm for a prosocial world of networked avatars was infectious. Or maybe I had just finally drunk the Silicon Valley Kool-Aid. Whatever it was, it now seemed to me that VR might just transform the world for the better—if only we could creatively harness its potential.

What, then, are the types of virtual realities we could create, and how should we go about doing it? People fly to my lab from all over the world to hear answers to those questions. One of the questions I get asked most often by companies trying to get into VR is, “What should we do?” My answer, of course, depends on the context. I have had hundreds of these conversations since 2014, when VR began to go mainstream. Here are three loose guidelines that have emerged and evolved from those conversations:

1. Ask yourself, does this need to be in VR?

I’ve come up with a few rules of thumb for how I think about appropriate VR use cases. First, VR is perfect for things you couldn’t do in the real world, but not for things you wouldn’t do in the real world. Flying to the moon like Superman is OK. Participating in virtual mass murder—especially if it is designed to be realistic—is not. This is a big deal. Everything we know about training in VR points to the realization that the medium is incredibly influential on future attitudes and behavior.