How do the roots in an aerogarden grow?

Once you put your seed in the rock wool pods how do the roots form and grow into the water?

On my first grow. I started my seeds in 1 inch rockwool cubes in aerated water until roots were growing out of the bottom of the cubes. Then I placed each cube with a seedling in its own 5 inch net pot filled with hydroton. The pots are now in my aeroponic system, which is a 1.3' square box per se that holds 4 of the net pots. Water sprays from a water pump into PVC pipe with mister nozzles all of which is inside of the box beneath the net pots.

In the beginning the roots were just in the hydroton but the hydroton is able to adsorb water in the many pores in the rock. In doing so the hydroton is able to move the water upwards to the roots until they are long enough to reach out of the net pots and grow long enough to enter the reservoir water. Here is a good link for more information on hydroton if you're curious. http://joemacho.hubpages.com/hub/What-is-Hydroton-The-Magical-Grow-Rocks

Thank you! @IHateBuyingWeed