At the mugdhah stage, if an incision is made in the embryo and the internal organ is dissected, it will be seen that most of them are formed while the others are not yet completely formed.
According to Prof. Johnson, if we describe the embryo as a complete creation, then we are only describing that part which is already created. If we describe it as an incomplete creation, then we are only describing that part which is not yet created. So, is it a complete creation or an incomplete creation? There is no better description of this stage of embryogenesis than the Qur'anic description, "partly formed and partly unformed", as in the following verse:
"We created you out of dust, then out of sperm, then out of a leech-like clot, then out of a morsel of flesh, partly formed and partly unformed." [Al-Qur'an 22:5]
Scientifically we know that at this early stage of development there are some cells which are differentiated and there are some cells that are undifferentiated – some organs are formed and yet others unformed.
(from "The Quran and Modern Science, Compatible or Incompatible?" by "Dr. Zakir Abdul Karim Naik" published by Darussalam)