Well, they stick with body heat. This means that you can successfully wear these with thin bras and FITTING TIGHT shirts that have built-in bras without headlight issues. However, they can and will fall off if worn under a loose shirt. If you do not wear a bra and your fitted/tight shirt isn't thick enough, you'll get the 'large areola' issue- the outline of the concealers are noticeable. I feel like I'm doing a lot better letting my chest grow naturally without being constricted by padded bras, but no- I can't just wear a baby tee or backless dress with no bra and get away with it.