In the first chapter of the third SItE notebook,” Quaderno di Ecologia”, the topic of the harmfulness of cigarettes to the environment is introduced. Cigarette filters and smoking products are known to be a serious environmental problem because they are toxic and dangerous. The environmental hazard is generated by the presence of residues of toxic substances such as polycyclic aromatic hydrocarbons, heavy metals, pesticides and nicotine in tobacco, which are retained by the discarded filter with the cigarette butt. Following rainfall events, these substances may be leached from the butts and contaminate soils and/or surface water bodies. Ecotoxicological studies have revealed that chemicals released from butts are highly toxic to aquatic organisms including nicotine and ethylphenol. Inspired by the publication, Daphnia magna specimens, reared at the University of Milano Bicocca, were delivered to Prof. Moccaldi's institution and they were reared by her first-class students in dechlorinated tap water in common jars, with 20 individuals per vessel, and they were fed with a spirulina and yeast solution every two days. The experiment comprised the exposure of test organisms to water extracts of cigarette butts that had been collected in the square in front of the school building. The volume of water employed in each experiment was a minimum of 2 mL per organism, in accordance with the established guidelines. Students have recorded each step of the activity, and they have read up on the toxicity of butts on the SItE notebook. The activity has been very useful because it has allowed students to understand how butts can be dangerous, but also to study science and maths topics in a more effective way. Students’ approach to nature, their expectations and impressions have been collected through validated tests.