The narrator calls stem cells extraordinary. Why does she use this term to describe these cells?

Stem cells are called extraordinary by the narrator because stems cells which is mostly gotten from bone marrow is use in medicine for regeneration and repair of damaged tissues and organs. It is use to correct part of organs that is not working properly. It has been use for treatment of diseases over the years.

Explanation:

Stem cells are special human cells that have the ability to develop into some specialized cells which can be used to regenerate and repair damaged tissues and organs.

Stem cells can be use to replace tissues that has been damaged through diseases and it has been use for treatment of different type of diseases over the years.