With Tamara we began collaborate 20 years ago when she became the director of NIB. As an expert in cancer research, she recognized the importance of genetic toxicology, which was in Slovenia at that time completely neglected. All cancers begin in cells. It starts with genetic changes in one cell or a small group of cells. These changes are the consequence of mistakes during the DNA replication and cell division that occur spontaneously whereas exposure to genotoxic chemicals increases their frequency. Exposure to genotoxic chemicals is associated with environmental pollution with anthropogenic and natural contaminants as well as dietary contaminants. To prevent the consequences it essential to recognize genotoxic compounds and restrict their use. Exposure to certain genotoxic compounds is unavoidable, but the consequences may be reduced by natural antimutagens. Our major achievements of the 20 years research will be presented.