Investigating Earth Systems (IES) is an Earth science curriculum for the middle grades (6th-8th grades). Inquiry and the interrelation of Earth systems form the backbone of all IES activities. There are five key scientific concepts that underlay Earth Science in general and are stressed in particular in all nine Investigating Earth Systems modules: Earth is a set of closely linked systems; the Earth's processes are powered by two sources: the Sun and Earth's own inner heat; the geology of Earth is dynamic, and has evolved over 4.5 billion years; the geological evolution of Earth has left a record of its history that geoscientists interpret; and we depend upon Earth's resources. Supported during its development by the National Science Foundation, one link is to the publisher's website and another is to the project site.