"The popularity of lightweight bras in China today echoes the 'natural breasts movement' of nearly a century ago. "

Sixth Tone reports:

Back then, beauty standards favored flat over busty: Many Chinese women bound their chests with white cloth or wore tight vests. Small so-called lilac breasts — as well as tiny feet — had long been the stuff of Chinese men’s sexual fantasies. On Women’s Day in 1927, a group of sex workers demonstrated naked in Wuhan, now situated in central China’s Hubei province, to protest breast binding. The year after the Wuhan demonstration, the government banned breast binding nationwide for health reasons, as it had done for foot binding more than a decade earlier....

Lingerie wasn’t something people talked about publicly until the 1990s, when modern advertising once more redefined society’s feminine aesthetics — this time favoring large bosoms.... But the tide is turning again — spurred in part by rising feminist awareness — and many young Chinese women are no longer ashamed of their small breasts...

“We are probably the first Chinese [underwear] brand that uses models with small breasts — in the past, every brand would look for models who had a ‘career line,’” Liu says, referring to cleavage enhanced by push-up bras that supposedly lead to smoother career paths in male-dominated offices.

But the lightweight bras, without padding, present the problem of showing nipples, which, we're told, is "still taboo" in China, but:

Mao, the public relations officer [at a retailer of non-padded bras], solves the problem by opting for thicker clothes whenever she wears a bralette. But she thinks visible nipples will gain acceptance at some point. “I’ve seen Rachel’s nipples on ‘Friends’ popping out many times,” she says.