 As much as these achievements of genetic analysis pushed the gene in the biochemical or molecular domain, they were not able to elucidate the chemical nature of the gene and its immediate action. This required other experimental systems, which began to take shape in the 1930s to 1950s (Morange 2020, Part One). For instance, Max Delbrück (1906–1981) and others turned to T-phages (viruses that infect the bacterium e.coli) because they assumed that viruses were essentially “naked genes”. While these researchers were able to show that genetic phenomena (mutation, exchange of genetic material) were present in viruses and bacteria as well and to achieve higher resolution of analysis, this work remained as formal as Drosophila genetics. It was only through integrating new technologies from physics and chemistry into the new experimental systems that microbial genetics led to molecular genetics. Results from biochemical work in biomedical microbiology and from work involving radioactive isotopes to label biological molecules provided evidence that DNA might be the genetic material.