Despite growing research in the field of regenerative medicine, stem cell research has faced many [Page 700]difficulties to achieve therapeutic benefit. The biggest hurdle is the lack of knowledge about the signaling mechanisms involved in tissue repair and how the molecular and cellular factors interact with each other in the regeneration of tissue.

Learning about the development of certain organs may help in understanding the mechanisms behind behaviors of regenerative cells and their interactions with their surroundings. This article reviews embryology of the lungs and capacity of lung cells to regenerate and replace old or injured cells in certain conditions.