## **Core Concept**
Stem cells are **undifferentiated cells** that have the unique ability to develop into many different cell types in the body. They play a crucial role in growth, tissue repair, and maintenance. Stem cells can be found in embryos and adults, with embryonic stem cells being **pluripotent** and adult stem cells typically being **multipotent**.

## **Why the Correct Answer is Right**
The correct answer, **D. Undifferentiated cells that can give rise to several cell types**, accurately describes the fundamental characteristic of stem cells. This definition highlights their ability to **self-renew** and **differentiate** into multiple cell types, which is essential for their role in development and tissue homeostasis.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately describe stem cells.
- **Option B:** This option is incorrect because, although stem cells do have the potential to develop into various cell types, this option does not specifically mention their undifferentiated state or their capacity to give rise to several cell types.
- **Option C:** This option is incorrect because it inaccurately describes stem cells.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that stem cells have the potential to revolutionize medicine through **regenerative medicine** and **tissue engineering**. Their ability to differentiate into various cell types makes them valuable for treating diseases and injuries that currently have limited treatment options.

## **Correct Answer:** . Undifferentiated cells that can give rise to several cell types