What is the fine-grained topic of the following text: Jingjinji Metropolitan Region or Jing-Jin-Ji (JJJ), also known as Beijing-Tianjin-Hebei, is the national capital region of China.It is the biggest urbanised region in Northern China that includes an economic region surrounding Beijing, Tianjin, and Hebei, along the coast of the Bohai Sea. Only return the topic.
Jingjinji Metropolitan Region in China