Consensus was reached on seven core concepts of physiology using the Delphi method, including "integration," outlined by the descriptor "cells, tissues, organs, and organ systems interact to create and sustain life." This core concept was unpacked by a team of 3 Australian physiology educators into hierarchical levels, identifying 5 themes and 10 subthemes, up to 1 level deep. The unpacked core concept was then circulated among 23 experienced physiology educators for comments and to rate both level of importance and level of difficulty for each theme and subtheme. Data were analyzed using a one-way ANOVA to compare between and within themes. The main theme ("theme 1: the body is organized within a hierarchy of structures, from atoms to molecules, cells, tissues, organs, and organ systems") was almost universally rated as Essential. Interestingly, the main theme was also rated between Slightly Difficult to Not Difficult, which was significantly different from all other subthemes. There were two separate subsets of themes in relation to importance, with three themes rating between Essential and Important and the two other themes rating as Important. Two subsets in the difficulty of the main themes were also identified. While many core concepts can be taught concurrently, Integration requires the application of prior knowledge, with the expectation that learners should be able to apply concepts from "cell-cell communication," "homeostasis," and "structure and function," before understanding the overall Integration core concept. As such, themes from the Integration core concept should be taught within the endmost semesters of a Physiology program. [This article was written with Task Force.]