This animation has been made by the data taken from scans of a developing embryo. It shows that our face don't just grow, but fits together like a puzzle. The three main sections of the puzzle meet in the middle of your top lip, creating the groove that is your philtrum.
This whole amazing process of creating a recognisable human face happens in the womb between two and three month. If it doesn't happen then, it never will. (read more below)
In the series, Michael Mosley explains the process in more details as below:
The early human embryo looks very similar to the embryo of any other mammal, bird or amphibian – all of which have evolved from fish.
Your eyes start out on the sides of your head, but then move to the middle.
The top lip along with the jaw and palate started life as gill-like structures on your neck. Your nostrils and the middle part of your lip come down from the top of your head.
There is no trace of a scar; the plates of tissue and muscle fuse seamlessly. But there is, however, a little remnant of all this activity in the middle of your top lip – your philtrum.
This whole process, the bits coming together of the various elements to produce a recognisable human face, requires great precision.
To fuse correctly the three sections must grow and meet at precisely the right time in the womb.