The demo is the Creature Creator which will let you mess around with 25% of the body parts available if you choose just the free version.
However shell out USD 9.99 / EUR 9.99 and you can get the full edition - either one will let you use your early species for the full retail game out this September.
"We are thrilled to finally be putting the creative tools of Spore into the hands of players around the world," said Will Wright. "The amazing creations players design this summer will help populate the game universe we all enter when Spore ships this September, so in a sense, the Spore Creature Creator is the birth of Spore."
You can showcase your Darwinian creations to the World by streaming them to YouTube; also the Spore demo will be included in the SimCity Box out on June 23rd.
Clickto visit the official Spore website.