Complex sentence: Perhaps the most famous use of a diamond in jewelry is in engagement rings, which became popular in the early to mid 1900s due to an advertisement campaign by the De Beers company, though diamond rings were used to symbolize engagements since at least the 15th century.
Split into simpler sentences: Perhaps the most famous use of a diamond in jewelry is its use in engagement rings. This use became popular in the early to mid 1900s due to an advertisement campaign by the De Beers company, though diamond rings were used to symbolize engagements since at least the 15th century.