Across the United States, political leaders, educators, and business persons are issuing an urgent call for reform in STEM education (NGSS Lead States 2013). One important response to this call is Integrated STEM, which the National Governor's Association (2007, p. 7) says involves, "... an emphasis on design and problem solving in "intellectually messy" learning situations that weave together the disciplines… ." Weaving or connecting the instruction of two or more STEM disciplines together is a way to enhance the personal meaning students attach to learning in those disciplines. In order to illustrate how this is done, one of the authors, who is especially interested in the integration of engineering and science, starts by explaining that when designing instruction that meshes two scientific disciplines both of the disciplines should include three characteristics: (1) There should be a natural meshing of engineering and science inquiry processes without one discipline being subordinate to the other; (2) Second, authentic integration of science and engineering instruction occurs when the 5E Learning Cycle (Bybee et al. 2006) and the Engineering Design Cycle (ECDC; Asunda and Hill 2007) are integrated in a sensible way; and (3) The third characteristic of authentic science and engineering integration is a natural connection between the content of the science and engineering activities being integrated. This article then goes on to describe a fifth-grade integrated science/ engineering unit that was designed involving 5-ESS2-1: "Develop a model to describe the cycling of water through Earth's systems driven by energy from the Sun and the force of gravity." It reflects the belief of the authors that the integration of science and engineering instruction will enhance student learning in both domains. Developed in partnership with the group of co-authors, the article shares their experience implementing this fifth-grade integrated science/ engineering unit involving 5-ESS2-1: "Develop a model to describe the cycling of water through Earth's systems driven by energy from the Sun and the force of gravity." The unit reflects the authors' belief that the integration of science and engineering instruction will enhance student learning in both domains as it chronicles each day of the seven day unit's progress.