Cartoon Network has put up a short, informative video about the basics of the Gems’ physical natures, by Ms. Florido and voiced by the show’s voice actors.
It doesn’t contain any information that can’t be gleaned from watching the show: Gems are their gems, which project what is effectively a hologram but with mass. If this form is damaged it is released so the Gem can focus their energy on regenerating, but if the gem itself is damaged things get “weird”.
Most importantly, we now know where the funny little bumper with Garnet chasing Amethyst comes from. 🙂
Anyone who can’t watch it on CartoonNetwork.com can watch it here.