This document discusses business opportunities in water and sanitation products and services for the bottom of the pyramid (BOP) market. It outlines that BOP markets have large volumes but low margins, weak institutions, and are difficult to access. Successful products and business models catering to the BOP are affordable and accessible, functional, high quality, sustainable, and enable local partnerships and production. The document provides examples of proven products like affordable ceramic water filters and outlines steps to take such as understanding the local context, field testing, and going to market through awareness, availability, affordability and acceptability.