Emil Chr. Hansen (1843-1909) was employed in 1879 as a constituent principal of the physiological Department of the Carlsberg Laboratory after performing his doctorate at the laboratory. Already in 1883, Hansen had his scientific breakthrough with the purification of yeast from individual cells isolated under the microscope. The method was also an immediate industrial success, with both Tuborg in Hellerup and Carlsberg in Valby having solved major problems with wild yeast; Within a few years the method became predominant worldwide. The short distance which in this case was from basic studies to practical application will be discussed in the context of descriptions of past and later examples of the history of microbiology.