You've been rocking — get ready for rolling. Between now and your baby's sixth month, she'll learn how to roll over. Active infants who love to stiffen and arch their backs are likely to roll over sooner than mellow babies, who are more content to lie on their backs and enjoy visual pleasures all around. Both types of babies will probably practice getting ready for this big rollover move by wiggling from side to side on their tummies. That's why it's a good idea to make sure your baby has plenty of "floor time" — opportunity to lie on the floor (or on a blanket on the floor or ground) to stretch out and play with you. She can't practice rolling if she's in his car seat, swing, bouncer, or sling all day long. You'll likely see your baby start a "mini-pushup" and then kick herself over onto her back. Eventually she'll be able to flip over onto her tummy again too. Your baby is also probably able to sit upright when propped by blankets or pillows. If she can do this for short periods without slumping forward or immediately toppling to the side, by all means let her enjoy the new views that come with sitting upright in a stroller or next to you on the sofa. (Take care not to leave a propped infant unattended. Even a seemingly stable pre-sitter can topple over.) From Babycenter.com