Narrator: Drifting along with countless single celled organisms, we feel the tug of a current. In the wonderland within, this sponge's cells all work for the common good. But they do it in wildly different ways. As the current draws us on, we pass sponge cells that are making new spicules.

[music playing]

The walls themselves are treacherous. They can simply engulf their unfortunate prey.

[music playing]

As we are drawn through ever narrower passages, the current slows until we burst into one of the sponge's millions of tiny beating hearts. These are choanocytes, cells whose whip like flagellae powers the pump. The flow quickens again, as it whisks us away through the labyrinth of canals that lead out into the sponge's central cavity.

[music playing]

What once seemed barely alive, is actually a living animal, more complex than we could have imagined.