From where are stem cells obtained

please help and make the answer simple

If you mean undifferentiated stem cells, in other words stem cells that are capable of becoming any type of cell in the body, they can only be obtained from fertilized eggs in the very early stages of development, before DNA can program them to be muscle or bone or nerve or any other specific type of cell. Once they are programmed, they cannot be deprogrammed.
Stem cells can also refer to bone marrow, but this is different. Stem cells in bone marrow make red cells, white cells and platelets; it is not the same issue as embryonic, undifferentiated stem cells.