A Virtual Scene is a segment of a video. Because it is essentially a start and end time for another video, a Virtual Scene does not take up any more hard drive space.
Metrixstream has an advanced thumbnail engine that not only resizes images on the fly, but also can quickly get thumbnails from anywhere inside your videos. This entire process makes creating virtual scenes extremely easy because you don't have to watch any video ever. It is much faster to just get thumbnails of what the video contains so you can quickly choose what portions to trim off and what portions to include in your new scenes.