Flavonoids are plant pigments found in fruits, vegetables, tea, flowers and wine. They are even more present in everyday life and it is of importance and significance to investigate their roleup on organisms. Naringenin is a flavonoid that belongs to the group of flavanones. Its effect was monitored on a hyda – algasymbiosis. As test organisms were used: Hydra viridissima Pallas, 1766 and Hydra oligactis Pallas, 1766 as well as endosymbiotic algae isolated from the hydra host Mychonastes homosphaera (Skuja) Kalina and Punčochářová, Desmodesmus subspicatus (Chodat) Hegewald and Schmidtand, related free – living species Chlorella vulgaris Beij. Morphological and cyto – hystological analysis was made using concentrations of 0,2 gL−1, 0,25gL−1 and 0,3 gL−1 of naringenin and it was determined that the concentration of 0,25 gL−1 does not favor the growth of organisms. Mortality, budding, mucus secretion, migration and contractions of hydra as well as viability of algal cells were monitored. Because of the possibility of changing and adapting the experiment in different temporal and spatial conditions and the availability of materials and accessories, its performance was suggested in school as a part of extra – curricular activities or school project. In order to investigate, if teachers would have proper pre - conditions for this kind of work, teachers of biology and chemistry in different schools and counties, were assigned an anonymous survey. Schools generally offer extra – curricular activities and they have appropriate tools to perform the proposed experiment.