OK, there are a few different issues here, I'll try and take them one at a time. 1) Why would someone do this? Well, lot's of reasons. Sometimes short video needs to be integrated with a Flash animation in a seemless way that interacts with and syncs with that animation. When that happens, it is often completely reasonable to embed the movie right into the flash. 2) Isn't the size huge? Well, that depends. It's a lot bigger than MPEG2 but that isn't always important. The PNG/JPG sizes can be pretty small in individual frames and since this is Flash you CAN stream the movie. 3) Whais the limitation? A Flash movie has an absolute limit of 16000 frames or so. Also, the way Flash draws the screen means that you will NOT be able to push 640x480 at 30fps or anything silly. 4) How do I do it? Any number of ways, but there IS an emerging set of applications dedicated to this problem. One of the best ght now is Flix from Wildforms. If you head over there they have demo's online. Enjoy!