Along with other microscopic organisms (dinoflagellates, diatoms, bacteria, etc.), we become a tiny particle and are pulled through the canals of a sponge. Along the way we learn that sponge cells catch food and make spicules(microscopic structures that help support the sponge's body). We are swept into the heart sac of the sponge where choanocyte cells with beating flagellae produce the current that eventually carries us out of the sponge body. [2:19]