These plants are like astronauts on my windowsill--way out of their element, but doing fine. They have no soil, only water. The onion came from the grocery store, but was forgotten in a bag. Once I saw how much it had grown, I decided to keep it around. Eventually I'll pot them both, but for now I enjoy watching them.
I am continually amazed at plants' ability to build their bodies out of air. They take in atmospheric CO2 and use it to create more complex molecules like cellulose. Thus, the spider plant on the right has been able to nearly double in size using only light, air, and water.
Read more about it here.
Photo by Michael McDevitt