The Institute of Microbiology was founded on March 7, 1947 by the world-famous Bulgarian scientist Prof. Stephan Angeloff, Member of BAS, who had been its first director for 15 years.The foundation of the Institute of Microbiology realized the necessity for a formation of a research center with national importance, which to carry out contemporary investigations in rapidly developing and prosperous branches of microbiological science. Five units were founded at first in the Institute: bacteriological (medical, agricultural and industrial bacteriology), protozoological, virological (investigation of viruses and viral diseases in man, animals and plants), immunological and biochemical. The initial period in the development of the Institute (1947 - 1962) was connected with the studies of the actual after the Second World War infectious pathology of domestic animals and humans under the direct leadership of Prof. S. Angeloff and his first collaborator Prof. Ilia Kujumgiev