What is the fine-grained topic of the following text: Founded in 2000 as CGNU following a merger between the Commercial Union and General Accident Group and Norwich Union, Aviva adopted its current name in 2002 and has quickly grown to become the sixth largest insurance company in the world, with a presence in more than 25 countries serving an incredible 53 million customers. Only return the topic.
Aviva Insurance Company's history and growth