What are stem cells?

Stem cells are defined as undifferentiated cells that possess the remarkable ability to differentiate into various cell types. This characteristic is fundamental to their role in development and tissue repair. Stem cells can either be totipotent, meaning they can develop into any type of cell in the body, or pluripotent, which allows them to differentiate into many, but not all, cell types. Because they remain undifferentiated, stem cells have the potential to undergo numerous rounds of division and offer a unique resource for regenerating damaged tissues in the body.

In contrast to stem cells, specialized cells (as mentioned in another option) have distinctive functions and structures that are determined through the process of differentiation. Actively dividing cells refer to those that are currently in the process of cell division but do not encompass the capability to differentiate beyond their current form. Mature cells that have lost differentiation potential can no longer turn into different types of cells, which greatly limits their functional versatility. This difference highlights the unique nature of stem cells in biology, making them a critical area of study in potential medical therapies and regenerative medicine.