In this chapter, they discuss the concept of using a software system called the brain to keep track of what they've learned. They explain how adding information to the brain involves a different way of thinking and how they curate their email, mailing lists, and Twitter feed to find interesting content. They also talk about the process of deciding what is worth remembering and how they weave the information into context. The chapter highlights the benefits of the brain system and how it facilitates system two thinking and contextual weaving.