This lesson, presented by the National Nanotechnology Infrastructure Network, introduces the concept of water purity. In this activity, students will test a sample of water collected from a local water supply and test its purity and evaluate its safety for consumption by looking for pollutants. Before starting, students should have a grasp on how to convert nanoscale measurements. This lab will take two 50 minute classroom sessions. Teacher Preparation Guides, Student Guides, Water Filtration Presentation, and Next Generation Manufacturing Standards for this lesson are included.