Once they have spotted their reflection, the dolphins use it to examine parts of their body they can't usually see, such as skin marks and the inside of their mouths.

The patient receives small skin marks to guide the placement of treatment fields.

The starchy tuber has a thin, smooth skin marked with some cracks.

Skin marks such as tattoos could reveal much about their history.

These uncertainties can be caused by internal movement (for example, respiration and bladder filling) and movement of external skin marks relative to the tumor position.