A term sometimes used for the embryo or ovum from the stage of fertilised egg (or zygote) up to the stage of the morula. During this time any of the cells of the fertilised ovum can develop into a whole new embryo -- they are totipotent. As it becomes a blastocyst a proportion of the cells (the inner cell mass) commit to producing the embryo proper, while the remaining majority are destined to form trophoblast. Distinguishing pre-embryo from loose use of the term embryo has some value when debating the morality of embryo research, but it is not universal practice.