And your baby? Pooping doesn't scare him anymore. He's got the basics of eating down, and he's starting to get the hang of sleeping. He's discovered that there are two very nice people in his world whose sole purpose is doing whatever it takes to keep him happy. For the 3- to 6-month-old, life is good.

During the 3 to 6 month period, your baby's main developmental task is to form relationships, says Beth Teitelman, Director of the 92nd Street Y Parenting Center in New York City and co-author of Wonderplay: Interactive and Developmental Games, Crafts and Creative Activities for Infants, Toddlers and Preschoolers. "What she's learning right now is that the world will meet her needs, if she expresses them," Teitelman says. "And the world is you, at this point."

Communication and Interaction
Your baby is getting interested in the world around her. Mirrors are particularly fascinating. "She loves to look at herself in the mirror," says Cassandra Lott of Williamsburg, Penn., when describing her 6-month-old, Georgia. "She plays a sort of game with my dad where he takes her to the mirror then pulls her back, then close again."

Babbling (repeating nonsense syllables) may begin. Susan Attiyah, of Glendora, Calif., tells the story of putting her 4-month-old down in an empty room for his nap. "My little 4-month-old son woke up and all by himself realized that if he would make a sound it would echo back," Attiyah reports. "He spent 30 minutes talking (well, baby talking) and hearing it echo back to him and then he would giggle."

Your baby will let you know when you’re doing something she likes by smiling, laughing and squealing in delight. She's also learning how to tell you when playtime is over. "Respect the baby's cues," advises Teitelman. If she's turning her head away or getting agitated, give her the down time she's telling you she needs.

The baby's new awareness of the world and the most important people in it -- his parents -- means that the first bouts of stranger awareness and anxiety often occur during this period.

Motor Skills and Development
Your baby is not a helpless newborn anymore. He's beginning to learn to control his body and his movements. By 6 months, he will be lifting his head, holding it steady and doing modified push-ups. He'll probably begin rolling over at some point during this period. He may enjoy sitting up, and may actually be able to sit up without support.

Some babies start pulling up to stand near the end of this period. And some are early crawlers or creepers. "She is already crawling, or should I say hopping, across the living room," says Elizabeth Ferree, of Yuma, Ariz., of her 6-month-old. "Our ground is pretty hard so I do have to watch her."

Your baby will learn to hold objects like small toys or rattles, and she'll learn to reach for things she wants. By 6 months, some babies will be able to pass objects from hand to hand.

Eating and Sleeping
Whether you're breastfeeding or bottle-feeding, the AAP recommends that babies not start solid foods until 4 to 6 months of age.

At 3 months, the average baby takes between 4 and 6 ounces at a feeding and feeds seven times a day, for a total of 30 ounces of milk. This amount will increase slightly through the fourth and fifth months, then go back down to about 30 ounces as the baby starts solid food.

As the baby becomes more interested in the world around her, new breastfeeding challenges may arise. She may be distracted during feedings. And she may even whip her head around to look at something across the room -- without letting go of your breast first! "If distraction becomes a problem, try to be in an environment with as little distraction as possible when you nurse," advises Carol Dittbenner, R.N., a lactation consultant in Roseville, Minn.

Mothers who are returning to work and pumping breastmilk face another set of challenges. Angie Larson, of Minneapolis, Minn., went back to work three days a week when her daughter, Madeline, was 5 months old. She tried to pump, but ran into difficulty. "I'd send her with two or three bottles to day care and then try to pump, but she was running out of milk at day care and I couldn't keep up," Larson says.

Larson's problem is a common one, Dittbenner says. "It's a delicate supply and demand between the baby and your milk supply," she explains. "Normally the baby would be eating more often if they need more, and if you're still pumping twice at work when it should be three times, then you start getting behind." Good communication with your day care provider about when and how much your baby eats is essential. And you need a good quality pump, Dittbenner says.

By 6 months, most parents will find that the worst of the sleepless nights are behind them. Lott's Georgia sleeps from 9 p.m. until 8 a.m., usually only waking up once.

Doctor Visits and Immunizations
Your pediatrician will ask you to bring the baby in for checkups at ages 4 and 6 months. At these visits, the doctor will check your baby's growth and development, answer your questions (bring a list), and give vaccinations.

The American Academy of Pediatrics (AAP) recommends that babies be vaccinated for diphtheria, tetanus and pertussis (DTaP), haemophilus influenzae (Hib) and polio (IPV) at both of these visits. Depending on your family's situation, your pediatrician may also recommend a hepatitis B vaccination for your baby at one of these visits. That's three shots to those tender little thighs. If you want to vaccinate but can't stand your baby's pain, talk to the pediatrician about using a cream to numb the area where the shots are given.

Age-appropriate Toys and Games
At this age, you're still your baby's favorite and most important toy. "It's not about things," says Teitelman. What your baby needs most is interaction with you. Teitelman advises lots of cuddling, singing and just being playful when you do what you need to do. For example, when you hold, feed, change and bathe them.

As you and your baby learn new ways to communicate, you'll discover something you didn't think was possible: You're falling even more deeply in love with this tiny little creature! Don't worry too much about development, Teitelman advises. It will happen on its own. "Try to relax and not worry and just to enjoy," Teitelman says.