For thousands of years, women have worn supportive undergarments in some form or another. However, modern bras have only existed since the early 1900s. One modern bra style, the demi cup, allows support without completely covering the breasts.
Demi cup bras are shorter and shallower than conventional bras. Usually, the cup is cut to one inch above the nipple.
Demi cup bras are sometimes called shelf bras or balconette bras.
Demi cup bras are designed to lift the breasts and provide some coverage while leaving the top of the breasts exposed to show cleavage. They allow women to wear low-cut tops without exposing the bra.
Many push-up bras use the demi cup style because it flatters cleavage. Some are designed to push breast tissue towards the center of the chest to create the look of fuller cleavage.
A demi cup bra is not the same as a half cup bra. The cup of a half cup bra stops just above the nipple. The half cup bra gives some support while exposing cleavage. However, the half cup does not provide as much support as the demi cup.