During the Jurassic period (201 million to 145 million years ago), termites up to 15 mm long consumed and recycled vegetation and feces. Since then, termites have evolved into some 3,000 identified species, have colonized every continent except Antarctica, and are major contributors to nutrient cycling and vertebrate food webs (Shaw 2014). Termites' persistence through time is largely due to the symbiotic association of protists and other microbes that colonize the termite's gut. These "endosymbionts"--organisms living inside a host organism--allow the termite to digest cellulose from plant debris for nutrition. In return, the termite gut provides a stable environment in which endosymbionts can maintain homeostasis. In this article, students dissect a termite hindgut, observe and record the symbiotic relationship between the endosymbionts and termites, and investigate the responses of protists when their environment is disrupted. Students also learn about the interconnected relationships and processes that affect their own body and the world around them. The activity, which aligns with the "Next Generation Science Standards" (NGSS Lead States 2013; see box, p. 51), engages students in three fundamental biological concepts: "symbiosis," "homeostasis," and "osmosis."