Cardboard consists of a low-cost, DIY virtual reality headset that anyone can build, and a software platform that makes it incredibly easy for app developers to add VR support to their creations.
Essential reading: The best VR headsets
You can buy a headset from DodoCase, or the likes of the Archos VR Headset or the Freefly VR will do the job of creating a virtual reality experience, with your smartphone providing the visuals. Look for the Works with Cardboard badge.
Once you've got your headset set up, you'll want some experiences to test out. Here's our pick of the best VR-enabled apps you can find in Google Play right now.
Star Wars VR
We're not sure if you heard but there's a new Star Wars film out at the moment. If you're in the minority and haven't seen it yet or you just love anything to do with The Force Awakens, the Cardboard experience puts you in the role of a Resistance secret agent on Jakku, the desert world that features in the film. You can feel the VR force on your iPhone or Android phone.
Free, Star Wars
Google Cardboard camera
Google recently introduced the photography app that now lets you take 360-degree, virtual reality photos and view them through Cardboard. To take a suitable pic, download the app to your Android phone (iPhone support is coming), hold you phone and move it around in a circle. The app will do the rest, stitching together images and capturing audio. It even works with Google Street VR so you can add 3D locations to your favourite locations as well.
If you want a dose of news and documentaries, NYT VR is your app. Beginning with the 11 minute The Displaced and 5 minute Vigils in Paris, The New York Times promises to post new virtual reality stories "every month or so". A little slow in use but we're sure the bugs will be ironed out. It's available for both iPhone and Android.
Free, The New York Times
Tilt Brush Gallery
VR drawing apps haven't made it to Google Cardboard yet – it was one of our favourite demos on HTC Vive. But for now we have Gallery which lets you look around creations and basically watch them being drawn in the full blown Tilt Brush app. Magic.
Free, Skillman & Hackett
Google has updated its Street View app for iOS and Android and okay, okay, it's not strictly VR but it is 360 degree images from around the world that you can look around. Virtual tourism, here you come. Just tap the Cardboard icon anywhere that Pegman can access.
The North Face: Climb
A visually stunning, high production experience from Jaunt, this app lets you follow two The North Face climbers as they climb and base jump their way around Yosemite and Utah. We want to go to there.
Jaunt recommends a new 5-inch or 6-inch phone and some users have reported it isn't working, so try it out.
Immersing yourself in VR – even Cardboard – can be relaxing and this Lantern festival experience is a terrific example of precisely that. It's basically just scenes of lanterns floating on moonlit water (there's a day-night cycle) and off into the mountainous distance. Lovely.
Free, Oleksandr Popov
There are a few fun little VR games and Proton Pulse is a good'un. It's a neon, arcade style brick breaker that's amusing for a quick hit. It's not just a demo either; there are a bunch of levels and all proceeds go towards development of the devs' next game for VR Vanguard V. Also, give WAA! VR a download if you have a bit of cash to spare.
For something a bit sillier, download BeerBox. This AR-style game, if you can call it that, uses your phone's camera so make sure you're using it with a viewer that has a cut-out or one that can secure your phone without the faceplate.
You can choose to experience ten levels of being drunk and your view of what's in front of you blurs, doubles and moves slowly. Scary, but funny, stuff.
Free, Schulze Gipson
War of Words VR
Beautiful, poignant and possibly the best VR experience app so far, this wartime experience – based on the BBC series of the same name – takes you back to the battlefields of the Somme in 1916. You're treated to a reading of Siegfried Sassoon's controversial poem 'The Kiss', all the while surrounded by an incredible depiction of the horror – at one point you can even follow a bullet in slow motion as it strikes down a soldier.
It's a shame there's only the one poem available right now, let's hope an update lands soon – we didn't see one in 2015.
Free, Burrell Durrant Hifle
Creepy. Strange. Addictive. We're not sure we can tell you about Sisters without ruining the surprise.
Turn the lights off, plug your headphones into your phone and prepare to be utterly freaked out.
Free, Otherworld Interactive
Chris Milk worked with visual effects specialist Digital Domain, acclaimed film production company Annapurna Pictures/VRSE.farm and VR production company VRSE.works to create a photo-realistic, CGI rendered, 3D VR film that takes the viewer on a journey from one new beginning to another.
You start off at a beautiful lake where you watch a swarm of dragonflies do their thing and then things get a bit trippy. We won't spoil the ending.
Elsewhere in the VRSE app you can see Milk's other projects, including his series with the United Nations.
A must download for anyone wanting a bit of VR culture in their lives, Orbulus brings the work of the Photo Sphere community to life, putting you dead centre of some incredible landscapes and venues. You start off in outer space and select an orb that you like the look of, simply by holding your gaze on it.
You're then placed where the photographer was but, rather than seeing a flat image, you are presented with their location around you, whether that be a city by night or an art gallery by day, in 360 degree glory.
Titans of Space
Fancy having a little look around the solar system without leaving your living room? That's possible with this app, which takes you on a scaled down (1:1,000,000) tour around space, complete with 3D models and to-scale distances between planets and moons.
You can control the speed of the tour using either a Bluetooth control pad, or simply by looking and selecting menu buttons, and there's also a premium add-on that adds 50 minutes of narration.
Jack White: THIRD-D
Want to stand on the stage while the White Stripes frontman does his thing? That's exactly what this app does, with footage from all angles of Jack's performance of 'Freedom At 21' and 'Ball and Biscuit' at The Bleacher Theater in Boston, and 'Dead Leaves and the Dirty Ground' from the Red Rocks Amphitheatre in Morrison.
You can look anywhere you want – at the audience, at individual band members, at Jack White himself, at the sky – it's as if you were there. But with no chance of being hit with a cup of urine.
Free, Jaunt Inc
Want to test drive the Volvo XC90 without leaving your house? Sure you do and that's where this app comes in. The result of a partnership between the Swedish car giant, R/GA and VFX-studio Framestore, it's the focal point – quite literally – of the new SUV and packs in a trio of experiential videos.
Friday Getaway is our favourite – it kicks off on a track and within minutes you're zooming through mountains and fields. What's more, it works on any day of the week.
It would be amiss not to give an early mention to the official Google Cardboard app in this list. As well as teaching you the basics of virtual reality, it lets you fly around in Google Earth, take a Street View tour, examine a series of tribal masks, watch YouTube videos on a giant screen, enjoy a short animation of a mouse on a windy day and watch 360-degree video.
But the best feature is the ability to view photospheres captured with your smartphone's camera. By stitching together a series of photos taken in every direction, you can create a panorama that you can enjoy in your headset.
Free, Google Cardboard
There are relatively few virtual reality apps that use your smartphone camera to layer things on the world around you, but one of the best so far is Glitcher. It lets you superimpose nine different filters on the camera input, including selective colour, edge detection and Predator vision.
But the most impressive feature is voice control. Use the magnet switch and speak commands to flip between filters, record video, take photographs and even activate the flashlight. If you don't yet own a VR headset, you can also activate a non-VR preview by pressing the volume down button.
Free, Glitcher VR
Roller Coaster VR
You can't have a VR app roundup without including at least one rollercoaster themed one can you? The pick of a very big bunch is this one, which adds beautiful jungle scenery – and some water travel – to the equation as well.
Out of the apps and games that we've selected, this is also the VR app most likely to make you puke. You've been warned.