Dry ice is super cold. I wondered what would happen if I heated some water in the microwave to the boiling point, then poured it over the dry ice. It made a dramatic effect of flowing cloud and fog. Just for fun, I thought it would be cool to stick it in the bottom of our plant pot, to get a wondrous flowing fog effect around the plant stalks. Some people wonder if the vapor is harmful for plants, but in actuality, plants use CO2 to grow, and produce oxygen as a byproduct, so in my opinion, the plants love it. 2 years later the plant is still healthy and well with no ill effects from the experiment.