Complex sentence: Serene Highness (acronym HSH-- "His Serene Highness" or "Her Serene Highness") is a style used today by the reigning families of Monaco and Liechtenstein.
Split into simpler sentences: Serene Highness (acronym HSH)-- "His Serene Highness" or "Her Serene Highness". The style is used today by the reigning families of Monaco and Liechtenstein.