"Soap can be made by everything. You can see the world from a special angle through the tiny thing," says the 41-year-old.

Soaps on display are made by adding various ingredients, such as Japanese sake, coffee beans, volcanic ashes and even cow dung.

The designs and packing materials are also attractive. The bars of soap from Thailand are exquisitely sculpted in the shape of lotus flowers. A set looks like mahjong tiles played in China. Some soaps are wrapped in wool, bark or coconut shell.

"One can know the local culture by buying a soap produced locally," says Chen, adding that many producers put local landmarks, art and well-known historical figures and events on the package design of soaps.

Before the pandemic, Chen spent months traveling every year to find soap. It could be soap-related history, a special ingredient, a funny design or an art museum selling soap.

She recalls her tough journey to a Marseille soap factory, which produces the oldest hygienic cube soap in France. Chen searched for the soap in Marseille for two days and happened to meet a man who promised to guide her to visit the soap factory. However, when she arrived at the factory in a suburb and waited for hours, the man never appeared. Fortunately, she met a worker there and finally saw the whole producing process of Marseille soap.