This photo taken with scanning electron microscopy depicts an extremely small yet precise volume (i.e., nanolitre-sized) of crystallized decanoic acid. We are using these spots of crystalline acid to extract and preconcentrate, or soak-up, chemicals of concern like opioids from wastewater samples. This preconcentration step improves our ability to monitor these chemicals. By doing so, we can improve how we detect these harmful compounds and protect local watersheds.