**Core Concept:** The development of the human face involves a series of complex processes occurring in specific embryonic planes. These planes are essential for understanding the formation of facial structures and abnormalities that may arise due to disruptions in these planes. The face develops from different regions of the embryo, including the ectoderm, mesoderm, and endoderm.

**Why the Correct Answer is Right:**
The correct answer, **D.** The facial crests, describes the process of development in which the face forms from the lateral edges of the neural crest cells. These cells migrate and differentiate into various tissues, including bone, cartilage, and muscles. The facial crests contribute to the formation of the craniofacial skeleton, such as the mandible and the maxilla, as well as the muscles of facial expression.

**Why Each Wrong Option is Incorrect:**
A. The **A.** Medial process is not a correct answer as it does not describe the correct developmental process of the face. The medial process refers to the formation of the nasal processes, which are different from the facial crests involved in the development of the face.

B. The **B.** The facial crests develop from the lateral edges of neural crest cells, not the lateral edges of the somites, which are involved in the development of vertebrae and muscles of the trunk.

C. The **C.** The facial crests develop from the lateral edges of the somites, but this answer choice is incorrect as the somites are involved in the development of the vertebral column and muscles of the trunk, not the face.

**Clinical Pearl:** Understanding the embryonic development of the face is essential for understanding various facial abnormalities, such as cleft lip and palate, which can be attributed to disruptions in the developmental process of the facial crests.

**Correct Answer:** **D.** The facial crests, which develop from the lateral edges of the neural crest cells, play a crucial role in the formation of the craniofacial skeleton and muscles of facial expression. A thorough understanding of these developmental processes helps to recognize and manage various craniofacial abnormalities in clinical practice.