Stem cells are important to multicellular organisms because of their

ability to differentiate into other cell types during cell division i.e. totipotent nature

Explanation:

Stem cells are undifferentiated cells with the unique ability to develop into specialized cell types in the body during early life and growth through the process of cellular differentiation. When a stem cell divides, each new cell has the potential to either to remain a stem cell or become another type of cell with a more specialized function e.g muscle cell, red blood cell or a brain cell.

Stem cells provide new cells for the body as it grows, and replace specialized cells that are damaged or lost. This ability of stem cells to differentiate into a variety of cell types in an organism including embryonic tissue, is an important distinguishing factor. They have two unique properties that enable them do so:

1. They can divide over and over to produce new cells

2. As they divide, they can change into the other types of cell (cellular differentiation).