The broadest level of organization in the modern classification system used by biologists is called a domain.

Here's a breakdown of the levels:

* Domain: The highest level, encompassing the largest and most inclusive groups. There are three domains: Bacteria, Archaea, and Eukarya.

* Kingdom: A major division within a domain. For example, within the domain Eukarya, there are kingdoms like plants, animals, fungi, and protists.

* Phylum (or Division): A subdivision within a kingdom. For example, the phylum Chordata includes all animals with a backbone.

* Class: A subdivision within a phylum. For example, the class Mammalia includes all animals with fur or hair and mammary glands.

* Order: A subdivision within a class. For example, the order Primates includes monkeys, apes, and humans.

* Family: A subdivision within an order. For example, the family Felidae includes all cats.

* Genus: A subdivision within a family. For example, the genus Panthera includes lions, tigers, leopards, and jaguars.

* Species: The most specific level, referring to a group of organisms that can interbreed and produce fertile offspring.