Boundless' content is organized into a three-tiered hierarchy: chapters, sections, and atoms.


Chapters are the highest level of organization in Boundless content. For example, a chapter in our U.S. History book is "Ancient America Before 1492." A single chapter will be denoted by a number; for example, the "Ancient America Before 1492" chapter in U.S. History is Chapter 1.


Each chapter is comprised of several sections. For example, a section in the "Ancient America Before 1492" chapter is "Early Inhabitants of the Americas,” numbered Section 1.1.


Within each section is a number of atoms. An atom is the smallest, most basic level of our content and consists of full text, a one-line "brief," key points, and key terms. All of our actual text content resides on atom pages; chapters and sections do not contain any content. They are simply arrangements of atoms.

Each atom has a learning objective, content to support that learning objective, and associated assessment items to test that learning objective.

An example of an atom from the "Early Inhabitants of the Americas" section is "Migration to North America," Atom 1.1.1.

The Book Editor

The Boundless book editor allows an educator to customize their own copy of a Boundless book to suit the structure of their specific syllabus or course. Through a simple drag-and-drop interface, the book editor makes it easy to edit a table of contents—to reorder the content, to pull in new material from other subjects on Boundless, and even to add your own content.