For thousands of years people have understood something of microorganisms without suspecting their existence. Fermented foods and drinks are described in some of the early examples of recorded history.

Writings give clear advice about the use of disinfectants for mummies or
embalming bodies.The ancient Egyptians used a collection of substances to stop bodies of their dead kings and queens from putrefaying even though they knew nothing about microbes.
Ancient Greeks used sulphur to fumigate rooms and Hebrew law insisted that clothes from leprosy victims should be burnt. The history of microbial control is as long as the history of people.
People have known the effects of microbes for thousands of years. The rise of bread, beer and yogurt are the product of microbes. Even the most primitive societies could treat certain illnesses caused by microorganisms without knowing their existence.
Microorsganisms are so small that nobody had seen microbes until the invention of the microscope.

Spontaneous Generation is the hypothetical process, also called abiogenesis, by which living organisms develop spontaneously from mineral or decomposing organic matter, according to a theory adopted during Antiquity and the Middle Ages.
Following his earlier discoveries, Pasteur proceeded to investigate the origins of microorganisms responsible for fermentation. After numerous experiments and quarrels with his critics and detractors, he was finally in a position to declare, in 1862, that:

- Atmospheric dust contained microorganisms ready to develop and spread.

- Even the most putrescible fluids remained unaffected when shielded from contact with these germs.

- The concept of spontaneous generation had no scientific basis.

Science was making great progress, with research and experiments like those of Louis Pasteur discarding old beliefs such as "spontaneous generation". The discovery of more and more bacteria and their key role in known infections highlighted the fact that it was possible for people to be protected against them.