This chapter might be a little bit disappointing for some readers – for it deals mainly with sex between bacteria and unicellular organisms since we are interested in how sexuality came into being – the very first beginnings of reproduction based on two different sexes. The long way from exchanging some genes (sex factors) from bacteria to bacteria up to the highly developed  reproduction of mammals will be outlined in this chapter – of course absolutely against the background of the PRINCIPLE OF EXISTENCE. To our surprise we will discover that actually a little molecular mishap must have been the beginning of all sexuality in this world...