The Philips Avent natural response bottles are specially designed for moms who want to combine breast and bottle feeding for their newborns. The ultra soft, breast shaped nipple encourages a natural latch and mimics the feel of a mother's breast, making the switch between breast & bottle as smooth as possible for you and your baby. The bottles allow the babies to drink, swallow and breathe using the natural rhythm. The bottles come with a unique opening that only releases milk when the baby actively drinks.