Here's why:

* Stem cells are undifferentiated: They have the potential to become any type of cell in the body.

* Differentiation: This is the process by which a stem cell becomes specialized, acquiring unique characteristics and functions that define a specific cell type (e.g., muscle cell, nerve cell, skin cell).

Examples of differentiated cells:

* Muscle cells: Responsible for movement.

* Nerve cells (neurons): Transmit electrical signals throughout the body.

* Blood cells: Transport oxygen and fight infections.

* Skin cells: Protect the body from the environment.

Note: While stem cells are the primary cells that differentiate, other types of cells can also undergo some degree of differentiation under specific conditions.