This document provides guidance on writing the introduction section of a chapter. It recommends that the introduction establish the need for the study by identifying a gap in existing knowledge, explaining why the gap needs to be filled, and summarizing how the current study aims to fill that gap. The introduction should provide brief background on the research topic, the rationale for undertaking the study, and key references. It should be structured in three parts - what is known, what is unknown, and how and why the gap should be filled.