Dr. Robert Cahalan is Director of Sun-Climate Research at NASAs Goddard Space Flight Center in Greenbelt Maryland. He recently retired as Chief of Goddards Climate and Radiation Laboratory, and President of the International Radiation Commission. He has held several jobs related to climate change, and has been doing science research for more than 40 years. He loves science, designing and building scientific instruments, and using them to discover how the universe works. Bob says: Clouds are endlessly fascinating for their many complex and beautiful properties, and important for Earths climate because they control the flow of energy in the atmosphere, and the supply of energy to the oceans. At Goddard I designed a laser system with multiple views, like a bees eye, showing that it can see through clouds to measure their thickness, naming it THOR, for Thickness from Offbeam Returns. I have flown THOR over Oklahoma, Central America, and Antarctica, measuring clouds, ice, and snow. I discovered that clouds have an effective thickness depending on their fractal properties, an idea now used in global climate models.