At ten (10) weeks of gestation, the cells differentiate into muscle, cartilage, and Bone.

http://en.wikipedia.org/wiki/Anatomy_of_the_human_nose

At ten (10) weeks of gestation, the cells differentiate into muscle, cartilage, and bone. If this important, early facial embryogenesis fails, it might result in anomalies such as choanal atresia (absent or closed passage), medial nasal clefts (fissures), or lateral nasal clefts, nasal aplasia (faulty or incomplete development), and polyrrhinia (double nose).