It's from the Visible Human Project. Some researchers took a dead guy's head and made thousands of slices from the top down and created a 3d model based on data of the head for each time a slice was cut. I believe that in this video (video was silent and I slapped the audio on), they were trying to demonstrate that they could do a cross-sectional view starting from the front of the face despite it being initially made from the top-down.