Soon they'll take your doctor inside your body.

Since we decided to spice up the cave walls back at Lascaux, we have been obsessed with creating ever more lifelike and realistic images, and that includes 3D.

Whether it's a Hollywood gimmick or the next generation computer display, our visualization technology has reshaped the way humans and machines interact.

Tech companies like Apple are buying up patents to create glasses-free 3D displays.

So you can bet that 3D is still in our future.

But is it going to be like the movies?

Are we going to have free-standing, floating holograms, 360 degrees around, like in Star Wars?

R2D2 coming up and shooting out that image of Princess Leia from whatever and...

*Help me, Jonathan! You're My Only Hope!*

Okay, that's creepy!

No one told me we were doing that. Can that go away now?

Thanks.

We don't have the technology to make those kinds of holograms, and maybe we never will.

A lot of that's due to the bad information we've had about holography.

For example, do you remember when Tupac Shakur blew everyone's minds by showing up at Coachella 2012 in hologram form?

Yeah, see that wasn't a hologram. That was actually this really cool angled mirror illusion called Pepper's Ghost, which we've been using for more than a century to simulate hauntings.

So what exactly is a hologram anyway?

When you take a picture with a normal camera, you're really just recording a single splash of light across a two-dimensional surface, like film.

But a holographic camera, well, that uses a laser beam splitter to split into two beams of light.; you've got one that's just a clean reference signal, and another one that you've run over a three-dimensional object.

So you can measure all those nooks and crannies and create a light map of that object.

So could we ever get to that free-standing hologram?

Well, one way we might try is by using a lot of different projectors to project light into a cloud of fog.

Now, the fog would actually act as a three-dimensional movie screen, and particles within the fog would actually reflect the light back to us.

Maybe we're even going to come up with technologies we can't even dream of right now to make holograms possible.

But here's a paradox for you—when did 3D become a gimmick?

I mean, our world is in three dimensions.

It's 2D that's the gimmick.

We build machines in 3D, we play with our pets in 3D.

I think the ultimate human-computer interface is one where we just strip away all of that division so that our non-computerized reality and our computer experience are merged as one.

I mean, imagine that you are a tele-surgeon.

You've got a hologram of the patient in front of you. The actual patient is 100 miles away.

You want that to be as accurate and seamless as if you were actually in the room with a blade in your hand.

Or imagine how much easier your world would be if we could actually build the holographic interfaces you've seen in movies, like Iron Man, where you move the data around.

It comes to you—you're no longer playing in this two-dimensional space, it's playing in your world.

Holography might even restore sight to the blind!

You might be able to use a combination of gene therapy and special glasses that actually beam holograms back to your eyes to restore your vision.

And of course, holograms will play a big part in one of my favorite subjects of all time: space travel.

We can already simulate the elements of space travel using something like the CAVE2, which is at the University of Illinois in Chicago.

They've even taken footage from the Mars landings and they can give you a full three-dimensional simulation of walking around on Mars.

And in the far future, Mars colonists might get a little homesick, so then they just go ahead and jump into CAVE3, and visit sweet home Chicago.