Early biology was focused on the observation and classification of living organisms.

The ancient Greek philosopher Aristotle is often considered the 'Father of Biology' for his systematic study of plants and animals.

The invention of the microscope in the 17th century revealed the previously unseen world of microorganisms.

In the 18th century, Carl Linnaeus developed the modern system of binomial nomenclature for classifying species.

The 19th century was a revolutionary period for biology.

The cell theory, which states that all living things are composed of cells, was established.

Charles Darwin's theory of evolution by natural selection, published in 1859, provided a unifying framework for all of biology.

Louis Pasteur's experiments disproved the theory of spontaneous generation and established the germ theory of disease.

Gregor Mendel's experiments with pea plants in the 1860s laid the foundation for the science of genetics, though his work was not widely recognized until the 20th century.

The discovery of the structure of DNA by Watson and Crick in 1953 launched the era of molecular biology and genetics.