Makes sense now; it is an ascending animation of horizontal sections. Every time it went back to the beginning of the animation, I kept thinking 'cellulose'.
Some forms of imaging can only represent in narrow 2 dimensional range at a time, So you're only looking at "slices" at a time. When I saw the image the first thought in my mind after seeing it play once again was "eh... looks almost like an ultrasound of broccoli" especially since the OP mentioned green, had he not even mentioned that your guess would have been as good as mine.