Since 1998 when there has been published the obtaining of human embryonic stem cells, there is being discussed worldwide the ethical justification of such research. Criticism is focused on the manipulation with the source of such cells, the human embryo. In the article are considered the pros and cons in the utilization of embryos to those ends. Attention is focused on the statute of the human embryo applying Aristotelian philosophy, and in connection with perceiving the embryo as a source of biological material there is discussed the difference between the human being and the human person.

        Key words: embryonic stem cells - human being - human person - embryo - Aristoteles.