Every day we deal with chemistry in various forms, but sometimes we don't see that. An example is biosensors that help us to evaluate health conditions, monitor environmental pollution and ensure food freshness. The most well known (and most widely sold) is the biosensor for blood glucose measurement, used every day by people with diabetes. Understanding the processes behind biosensors can provide insight into the mechanism of chemical reactions, electrocatalysis and biomimetics. In this activity, a group of high school students, within the 'Researchers in Class' project from Fondazione Umberto Veronesi, manufactured and tested a paper-based glucose electrochemical biosensor, highlighting the easiness of fabrication and application.