Using chemiluminescence, forensic scientists can shed light on the case and show hidden traces of blood even after some time. Luminol is most often used to show traces of blood where iron from hemoglobin is used as a catalyst in the reaction. We can also use other metals as catalysts. In the following video, we used luminol and copper from a diluted bluestone solution to demonstrate the chemiluminescence effect. We prepared two solutions: a diluted solution of blue stone with hydrogen peroxide, which is a strong oxidizing agent, and a solution of sodium hydroxide, which forms a complex compound with luminol. After adding a few drops of luminol solution to the first blue stone solution, the electrons from the luminol complex are excited, which when returning to the ground state emit the light we see.