The way real memories work, from what we understand, is really complex. And it's an interconnection of different things and redundancy in the brain. So the idea of a memory existing as a little snow globe - the way we represent it in the film - is actually not scientifically accurate at all.

The idea kind of started with me just thinking about what would be fun to see in animation, you know - what have I not seen? For some reason, I got thinking about the human body and realizing, well, I've seen, like, traveling through the bloodstream and into the, you know, stomach and things.

So we can sit with Lee Unkrich and Andrew Stanton, and all the other folks and experience what the film is going to be like. And then we go away into a room, and we talk about what worked and what didn't. And then we take all of those findings and we do that whole process again.

There's something really emotional about not having any sound. That allows, I think, the audience to participate more actively and kind of imagine what are they talking about there?

Dr. Paul Ekman, who worked in San Francisco - still does - which is where Pixar Animation Studios is, he had early in his career identified six. That felt like a nice, manageable number of guys to design and write for. It was anger, fear, sadness, disgust, joy and surprise.

We found some scientists think that there are basically three emotions. Others went up to 27. Others had 16. Some were in the middle. So we were kind of left with no definitive answer to our basic question - how many are there?

It's like you run into this dark tunnel, trusting that somewhere there's another end to it where you're going to come out. And there's a point in the middle where it's just dark. There's no light from where you came in and there's no light at the other end; all you can do is keep running. And then you start to see a little light, and a little more light, and then, bam! You're out in the sun.