Heraldry
In the terminology of heraldry, the abyme is the center of a coat of arms. The term "mise en abyme" then meant literally "put in the center". It described a coat of arms that appears as a smaller shield in the center of a larger one (see Droste effect).
A complex example of mise en abyme is seen in the coat of arms of the United Kingdom for the period 1816–1837, as used by King George III. The crown of Charlemagne is placed en abyme within the escutcheon of Hanover, which in turn is en abyme within the arms of England, Scotland and Ireland.
The two-headed eagle in the modern coat of arms of Russia holds a sceptre topped by a similar eagle holding a similar sceptre.
Read more about this topic: Mise En Abyme