YouTube is home to several zillion videos, but until recently, only Android users could take advantage of Cardboard mode -- a split-screen view designed for use with Google Cardboard and other VR headsets.
This bears a bit of explanation, starting with how you actually activate the setting:
Step 2: Tap the three-dot "More" icon in the upper-right corner of the screen.
Step 3: Tap Cardboard, then insert your phone into your VR headset.
Presto! Assuming it's an ordinary video, Cardboard mode effectively gives you the equivalent of movie-theater viewing.
However, if you head to YouTube's 360 Videos channel, you'll find a huge collection of clips that really take advantage of Cardboard mode. That's because they were shot in 360 degrees, which is where the whole VR thing really starts to shine.
In fact, these videos are so VR-ready they have a Cardboard icon right on the main screen; no need to venture into the More menu.
This is just the latest step in Google's increased support for iPhone VR. Back in March, the company introduced a Cardboard-oriented SDK designed to make it easier for software developers to integrate 360-degree video.
Meanwhile, Google's I/O conference kicks off Wednesday, and if the scheduled VR at Google session is any indication, there's more VR news to come. (My prediction: "Google Cardboard" gives way to a bigger, broader "Google VR" branding.)