Biology is the study of life in general — every living thing, at every scale. Microbiology is one of its branches, dealing with organisms too small to see unaided: bacteria, archaea, fungi, protists and viruses. All microbiology is biology; most biology is not microbiology.
The core difference
A field and one of its subfields, distinguished by scale.
- biology — the study of living organisms of every kind.
- microbiology — the study of microscopic organisms.
The other main branches
Biology divides many ways: botany (plants), zoology (animals), genetics (heredity), ecology (organisms and environments), anatomy (structure), physiology (function). These overlap heavily — a microbiologist studying bacterial genes is doing genetics too.
The viruses question
Microbiology conventionally includes virology, though whether viruses are alive at all is genuinely contested: they carry genetic material but cannot reproduce without a host cell. The field includes them for practical reasons rather than because the definitional question is settled.
