Colored scanning electron micrograph (SEM) of squamous cell carcinoma (cancer) cells from a human mouth. The many blebs (lumps) and microvilli (small projections) on the cells' surfaces are typical of cancer cells.
Petri dishes are shallow dishes used in science experiments usually to grow bacteria or fungus. These experiments are often used to demonstrate to students what grows in the human mouth or under your fingernails. There is often an underlying message encouraging children to brush their teeth or wash their hands.
This is the range of emotion and expression that is possible with the human face. This guy is moving - mouth, eyes, eyebrows. A great headshot technique is to throw out words and get your clients to make whatever face they want to convey that word. It doesn't have to make any sense, and a lot of times there's a genuine smile that comes right after making the silly face.