Whenever you are working on a composition chances are very good that from time to time you're going to want to see how your animation or your comp is coming. You're going to want to see the animation at some point to get the timing down, to see if the special effects are in the right place and that kind of thing. So I'm going to talk about two different types of previews, the first is obtained by hitting the spacebar so as you see I'm at the very beginning of my timeline and I'm going to hit on my keyboard the spacebar. And then I'm going to stop it in just second, but I want you to see up here, it's telling us that its not in real time as its doing this. You'll see that it slows down on occasion. Now, it's telling us that its only generating at the moment 15.7 frames per second out of 30, because once again hitting the spacebar is going to give you this green bar here and as this green bar stretches out these frames are non rendered to your computer at least in After Effects, not as an output file. So when we scrub back and hit spacebar again it plays back in real time. So if the green bars tells you that these have been rendered in After Effects and can be viewed now in full speed. When it gets back to the gray area it's going to have to chug down a little bit and slow down to generate those frames for you. So once again as I rewind I can now see my animation in real time and it says up here its playing at 30 frames per second in real time. That's the spacebar preview. Interesting thing about this though, if I change anything, if I grab this dark solid here that I have my rein on and I move it, look what happens, it has to render all that again because I move that one element. If you move anything at all you will get this, that's very important to keep in mind as well. Fortunately if you have a powerful machine it really won't matter because the preview doesn't take that long, as you see its generating it pretty quickly. The other kind of preview that I want to bring to your attention is called a RAM preview and a RAM preview will allow us to playback in full speed here. So I'm going to click this button here, likewise what I could do is hit the numeric zero on my numeric keypad the zero key to play at full speed, its going really fast as you can see here. And it pretty much plays based on the RAM which will give you the name RAM preview. Normally I just go ahead and hit the spacebar because I can wait for it to go all the way through. But if you have a lot of RAM and you want to get a nice preview right away the RAM preview is the way to go. But like the other preview if I mov anything we have to start from scratch, so those are two ways that you might want to preview your footage as you work using the spacebar for a regular preview or you can play a RAM preview.