The classification system used in biology today is largely based on the work of Carl Linnaeus, a Swedish botanist, physician, and zoologist who lived in the 18th century.

He is known as the father of taxonomy, the science of classifying organisms. He developed a system of binomial nomenclature, which gives each species a unique two-part name (genus and species). He also established a hierarchical system of classification, grouping organisms into increasingly inclusive categories:

* Kingdom

* Phylum

* Class

* Order

* Family

* Genus

* Species

While Linnaeus' system is still the foundation of modern classification, it has been modified and expanded over the years as scientists have gained more knowledge about the relationships between organisms. Modern classification takes into account evolutionary relationships, and uses DNA and other molecular data to refine the classification of organisms.