By the beginning of the twentieth century , doctors knew that many diseases were caused by living microbes They knew about immunization and vaccine. Thanks to the efforts of scientists like jenner , pasteur  , koch and Ehrlich Lister, had taught them the valr of antiseptics, Known chemical disinfectants , such as carbolic acid, would kill germs , but they would also injure celltissues. How could harmful microbes be destroyed without at the same time injuring body tissues ?

In 1900 to a shipping clerk-Alexander Fleming-a career in science seemed like distant dream, Alexander was born on August 6 , 1881, the youngest son of an Ayrshire , Scottish farmer. He was able to complete High School but thenm his family's funds ran out. At sixteen he took a job as a shipping clerk and stayed there for four years . In 1901 , Alexander came into a small legacy which enabled him to continue his education , and on the advice of one of his brothers who was a doctor, he chose to prepare for a career in medicine.

Alexander did unusaually well in medical school along with rifle shooting , swimming , water polo and painting  after his graduation , his teache Prof.Wright asked him to join him in bacteriological reaserch , which he readily agreed.