Starseeds and Sailor Crystals
Starseeds and Sailor Crystals are the life of an individual -- our souls so to speak. They are what makes us, us, and how the Sailor Soldiers get their power.
In the manga human Starseeds are flame like and blow away easily. They are not eternal like Sailor Crystals. They are easily destroyed just like the bodies of humans.
Sailor Crystals are not easily destroyed. Without a body they still live on and the host can be reborn again and again just as long as their Sailor Crystal exists. Only chosen people have Sailor Crystals, while everyone else has a Starseed.
In the anime everyone has a Starseed, no Sailor Crystals exist -- but some have extra power and their shine doesn't fade away when taken from the body. Regular humans have regular Starseeds, when removed from the body they lose their shine and turn all black.
Some Starseeds, True Starseeds, don't lose their shine and ones that are extra powerful are also colored. Mamoru's was gold for example, Kakyuu's was red.
