Learn why clouds are critical to Earth's climate system and the role that they play in the water cycle. Play the Cloud Lab: http://www.pbs.org/wgbh/nova/labs/lab/cloud/ Find discussion questions for this video and other resources in the Cloud Lab collection on PBS LearningMedia: http://www.pbslearningmedia.org/resource/nvcl.sci.earth.making/the-making-of-a-cloud/