With support from National Aeronautics and Space Administration's (NASA's) Goddard Space Flight Center, Institute for Global Environmental Strategies (IGES) has developed educational materials that incorporate information and data from the Tropical Rainfall Measuring Mission (TRMM), a joint satellite mission between the United States and Japan. "Investigating the Climate System" is a series of five learning modules for grades 5-12 created by educational specialists along with TRMM scientists, and finalized by IGES for national distribution. Each module focuses on a different component of the Earth system--clouds, energy, precipitation, weather and winds. This module focuses on clouds. Appended are: (1) Resources; (2) Assessment Rubrics & Answer Keys; (3) National Education Standards; (4) Problem-Based Learning; (5) TRMM Introduction/Instruments; (6) Online Resources; and (7) Glossary. [This document was funded by the National Aeronautics and Space Administration (NASA) Tropical Rainfall Measuring Mission (TRMM).]