Candling is a method used in embryology to study the growth and development of an embryo inside an egg. The method uses a bright light source behind the egg to show details through the shell, and is so called because the original sources of light used were candles.
The technique of using light to examine eggs is used in the egg industry to assess the quality of edible eggs.
In ceramic applications, candling is a method used to slowly heat up the kiln and the ware inside the kiln in order to dry the ware or heat before firing.
In the legal profession, candling is a colloquilism used to describe the procedure of submitting a party or criminal defendant to a psychological evaluation for evidentiary purposes.