Stem cells act as building blocks of our tissue, blood and immune systems. They can be derived from bone marrow, embryos and the blood that remains in the umbilical cord after a baby is born. According to Indian Council of Medical Research (ICMR) guidelines, only embryos up to 14 days old can be used for therapy and they should not be generated for the sole purpose of obtaining stem cells. And only surplus or spare embryos can be used after obtaining the consent of parents.