Abstract: Stem cells are undifferentiated cells with the ability to proliferate and convert
to different types of differentiated cells that make up the various tissues and organs in the body.
They exist both in embryos as pluripotent stem cells that can differentiate into the three germ layers
and as multipotent or unipotent stem cells in adult tissues to aid in repair and homeostasis. Perturbations
in these cells’ normal functions can give rise to a wide variety of diseases. In this review,
we discuss the origin of different stem cell types, their properties and characteristics, their
role in tissue homeostasis, current research, and their potential applications in various life-threatening
diseases. We focus on neural stem cells, their role in neurogenesis and how they can be exploited
to treat diseases of the brain including neurodegenerative diseases and cancer. Next, we explore
current research in Induced Pluripotent Stem Cells (iPSC) techniques and their clinical applications
in regenerative and personalized medicine. Lastly, we tackle a special type of stem cells called Cancer
Stem Cells (CSCs) and how they can be responsible for therapy resistance and tumor recurrence
and explore ways to target them.