There isn't a universally agreed upon system for dividing science into just three main groups. However, a common and helpful way to categorize science is based on the nature of the subject matter being studied:

1. Physical Sciences: This group deals with the study of non-living matter and its behavior. It includes:

* Physics: The study of matter and energy and how they interact.

* Chemistry: The study of the composition, structure, properties, and reactions of matter.

* Astronomy: The study of celestial objects and phenomena.

* Geology: The study of the Earth's structure, composition, and history.

* Meteorology: The study of the Earth's atmosphere and weather.

2. Life Sciences (Biology): This group focuses on the study of living organisms and their interactions. It includes:

* Botany: The study of plants.

* Zoology: The study of animals.

* Microbiology: The study of microscopic organisms.

* Ecology: The study of the interactions between organisms and their environment.

* Genetics: The study of heredity and variation in living organisms.

3. Social Sciences: This group explores human behavior, interactions, and society. It includes:

* Psychology: The study of the human mind and behavior.

* Sociology: The study of human society and its structures.

* Anthropology: The study of human cultures and origins.

* Economics: The study of how people make choices in the face of scarcity.

* Political Science: The study of government and political systems.

It's important to note that these divisions aren't always clear-cut. There are many areas where disciplines overlap, and new fields of study are constantly emerging. For example, biophysics blends elements of both physical and life sciences.