There are multiple possible applications of stem cells in medicine, from cell-based therapies for degenerative and dystrophic conditions, through novel approaches in cancer treatment, to in vitro organ printing. However, there are still several challenges that need to be overcame before stem cells therapies can be successfully introduced worldwide on a large scale. These include sourcing of stem cells, preventing their aberrant progression and ethical concerns regarding their use in animals and humans. Among the multiple stem cell types present in the human organism from the period of embryonic development to adulthood, this review focuses on the three types that gain the most attention in relation to modern research: embryonic stem cells, induced pluripotent stem cells and adult stem cells. There are a number of obstacles that need to be removed before these cells can be widely applied in clinical practice, including the choice of the perfect source of stem cells, full elucidation of the mechanisms of stem cell differentiation and plasticity, and minimization of adverse side effect potential. Nonetheless, the focus of the scientific community on the topic of stem cells remains unhindered, bringing hope that all of the possible concerns will be addressed in the future.
