When will my baby take his first step or say her first word? During their first year, babies start to develop skills they will use for the rest of their lives. The normal growth of babies can be broken down into the following areas:

• Gross motor - controlling the head, sitting, crawling, maybe even starting to walk
• Fine motor - holding a spoon, picking up a piece of cereal between thumb and finger
• Sensory - seeing, hearing, tasting, touching and smelling
• Language - starting to make sounds, learning some words, understanding what people say
• Social - the ability to play with family members and other children

Babies do not develop at the same rate. There is a wide range of what is considered "normal." Your baby may be ahead in some areas and slightly behind in others. If you are worried about possible delays, talk to your baby's health care provider.

A newborn sleeps 12-20 hours per day, but don't let that fool you: your baby will go through enormous transformations in his first month. Your womb was safe, warm, dark, and quiet. Now your baby has to adapt to the outside world, full of bright lights, noises, and unfamiliar sensations.

A newborn's most developed sense is touch and least developed sense is sight. Your baby will want to focus on things close up, especially your face. Be sure and make lots of silly faces. You'll never have a more appreciative audience! Because baby's stomach is tiny and can't hold very much food, and because he's growing so fast, he'll need to eat frequently: about every 3-4 hours. Breast milk contains beneficial bacteria that colonize an infant's digestive tract and protect against harmful bacteria.

At the age of 1-2 days, a baby's stomach can hold approximately the volume of a cooked chickpea. From 3-6 days of age, it can contain 1-2 oz, about the size of a grape. By the end of the first month, the stomach can hold food about the volume of a strawberry.

Your baby's very rapid mental development continues in the second month. Baby loves being held as well as being spoken and sung to. In response, she may start cooing back at you. It's the start of a great conversation! Your little one is beginning to anticipate certain events and may start to smack her lips just before feeding time.

Nutrients pass through your baby's small intestine more slowly than they do through yours, helping to ensure proper absorption and digestion. The intestine is designed for absorption, but because of that it's vulnerable to penetration by antibodies. Breast milk contains many different factors that offer protective benefits and stimulate an infant's intestinal surface to mature.

Docosahexaenoic acid (DHA) is an omega-3 fatty acid found in breast milk that's essential for proper functioning of the nerve cells of the brain. In the US, infant formula has been supplemented with DHA since 2001.

Your baby has changed so much from birth! In month 3 primitive reflexes are disappearing, giving way to movements under willed control. Ever-stronger muscles, along with explosive neurological growth in the brain and central nervous system, allow for better physical coordination and vision. Baby can raise his head and chest when lying on his stomach, bring his hand to his mouth, and swipe at objects.

Visually, your baby can focus on small objects now as well as recognize people and objects at a distance. As the eye's retinas continue to develop, he's better able to see the differences between colors, although he prefers bright, primary colors. He can easily track objects across a 180° arc.

Babies of this age are becoming more socially responsive. Your baby is expressive with his face and body and is probably starting to babble and imitate some sounds. He enjoys playing with others now and may cry when playing stops.

The volume of the human brain increases more during the first year than at any other time in life, almost tripling in size. Neurodevelopment proceeds from lower to higher brain centers, from the brain stem to the cerebral cortex, and from back to front.

In the fourth to seventh months your baby will make a huge developmental leap: she'll learn to coordinate her senses, like vision, hearing, and touch, with motor (muscle movement) abilities. This means your baby will be developing skills like grasping, raking at objects with her fingers, and bringing her hands to her mouth. Baby will start to push off the floor and learn to roll over as well.

Your baby's circulatory system will be working hard to provide rapidly growing tissues with the nutrients and oxygen-rich blood they need. A newborn's heart beats as fast as the heart of a strenuously exercising adult, about 120 times a minute, and will double in size during baby's first year of life. Many different nutrients, including protein, lipids, vitamins, and minerals, are essential to support the growth and functioning of your baby's circulatory system.

Beneficial bacteria like bifidobacteria in the infant intestine block the overgrowth of harmful bacteria, boost immunity, and aid digestion. Bifidobacteria are present in breast milk, and their growth in the intestine is supported by prebiotics in formula.

Big news! Somewhere around months 5 and 6, your little one will develop the ability to sit unsupported for up to 30 seconds or more. He'll be able to sit in the tripod position, supporting himself with one arm, for longer periods of time. Your baby is also developing the ulnar-palmar (mitten) grasp technique. He needs to use this method of holding things because babies of this age can't yet use their opposable thumbs, that is, grasp objects by moving their thumbs around to touch their fingers.

Although the evidence is mixed, most experts still recommend you wait until your baby is 4-7 months old to introduce soft solids, like cereal and mashed bananas. During this time, your baby's intestines are in a developmental stage called closure, in which the permeable intestinal lining secretes an immunoglobulin called IgA. IgA acts like a protective paint, coating the intestines and screening out potentially harmful allergens that might create a food allergy in your baby.

The stomach's mucous membrane lining contains glands and pits that secrete digestive juices, which aid in the breakdown of complex food molecules like proteins.

By the end of the sixth month, your baby might sit without support and even be able to bear some weight on her legs. Babies often start babbling at about this age. Practice a little conversational give-and-take! Her liking for the soft solids you may have introduced will be aided both by teething, which usually begins about now, and by her newfound appreciation of salty tastes. Babies are born with a sweet tooth, but only at this age do they acquire a taste for salt.

And speaking of eating, healthy babies have a healthy amount of fat! Baby fat is different from adult fat. About 2-7% of your baby's weight is brown fat, which contains large amounts of mitochondria, the cell's "powerhouses." Brown fat generates heat and helps to keep your baby warm. It's concentrated in baby's back and the nape of the neck, as well as around her heart, lungs, esophagus, liver, and kidneys. Only very small amounts of brown fat remain in adults, mostly around the kidneys and aorta.

At 6 months a baby's brain weighs 1.2-1.4 lb, about the weight of an acorn squash.

As your baby's repertoire of movements expands, his muscular and skeletal systems are growing and developing, too. Your little one will extend in length by a whopping 50% in the first year! Baby's bones are thickening and elongating, while at the same time his muscles are strengthening, allowing for a more and more complex range of motion. Now, at 7 months, your baby may be able to put all his weight on his legs, an important milestone in the progress toward those first steps.

Baby's brain is growing by leaps and bounds as well. At about 7 months, a major breakthrough in cognition takes place: your baby begins to understand that things still exist even if he can't see them, a concept termed "object permanence." Playing hiding games like peekaboo reinforces this idea. Your baby's vision is much more mature and he can now see in full color.

Look out, world! Stepping up that already astonishing rate of growth and development, your baby may begin to crawl this month (if she hasn't already)! To nourish the bones that support all the new and exciting activity, your baby needs a balanced diet that includes calcium and phosphorus, critical for bone growth, along with protein and other nutrients. Vitamin D must be present for bones to absorb key minerals.

To crawl (and later, to walk), your baby needs more than bones and muscle: she needs balance. This comes from your baby's vestibular labyrinth, a part of her inner ear that includes the semicircular canals and the otolith organs. The otolith organs contain a layer of tiny calcium rocks called otoliths that lies on top of a layer of gel. The labyrinth wall where the gel layer attaches is full of hair cells. When your baby moves her head, it causes the gel layer to shear, and that movement is sensed by the hair cells. This information is conveyed to baby's brain and allows it to make corrections to her balance.

Upper respiratory infections are the most common causes of illness in childhood. Bronchitis is an inflammation of the main air passages to the lungs, the bronchi. Bronchitis may be acute (short lived) or chronic, meaning that it lasts a long time and recurs often. Acute bronchitis usually is caused by viral or bacterial infections. Chronic bronchitis generally is due to long-term exposure to irritants like cigarette smoke.

When it is severe enough to require hospitalization, respiratory illness greatly increases the risk of childhood asthma.

Fortunately, at 9 months your baby's immune system has developed and is better able to fight infection than during the first months of his life. Lymph nodes and vessels are major components of his immune system. Lymph nodes are bundles of lymph tissue found throughout the body that collect and break down toxins and other waste products. Lymph vessels transport lymph, a clear fluid that comes from the spaces between cells throughout the body. Other important components of your babyâ's immune system include macrophages, white blood cells that surround and digest pathogens such as bacteria and fungi.

The areas of a baby's brain that control motor skills (movement) mature in a predictable sequence. The earliest areas to mature control the head and neck muscles. Then motor control of the torso, arms, and hands develops. Finally, the areas controlling the legs mature. Now, between 10 and 12 months, your baby's legs are, well, kicking in. Most babies of this age can crawl, sit without support, pull themselves up to a standing position, and cruise along the furniture.

Other areas of your baby's burgeoning brain are keeping pace with her motor development. She's increasingly curious and is probably imitating your actions, like talking on the phone. Since her birth, baby's digestive system has become able to carry out increasingly complex digestive processes, and she can now eat a wide variety of cereals, vegetables, and fruits. At 10 months she can start to eat meat as well, a valuable source of both protein and iron.

There's so much your little one can do! Although it takes years for movement patterns to be perfected, his greater motor abilities mean he can now use a pincer grip (thumb and forefinger) to hold objects, make music by banging a drum or playing a xylophone, dance to a tune (maybe with a little help from you), and even sing along. Improved hand-eye coordination allows him to feed himself finger foods. Give your baby a wide assortment of foods, both for varied nutrition and to help him appreciate different tastes.

His language abilities have evolved, too. Your baby probably responds to simple requests and knows the names of familiar objects and people, although he understands much more than he can verbally communicate at this point, and that can be frustrating for him. You can help your little one's speaking ability if you pronounce words correctly rather than using baby talk with him.

Your baby is 1 year old! Each baby is unique and develops in her own way and at her own rate. But no matter where your child falls in the developmental spectrum, it's amazing how much has changed since birth. Neurological development, in particular, has been astounding. Your baby's brain has almost tripled in size since day 1. Involuntary movement has changed to voluntary control, and immature vocalizing and crying have given way to actual speech. Once totally helpless, she is now very much her own person, with noticeable preferences and distinct personality traits.

Motor skill development has been phenomenal. It's likely your baby can now pull herself upright, handle a spoon with dexterity, and drink from a cup. She may walk a few steps or even be an adept walker. Standing upright and being mobile have given your baby a new sense of independence and, importantly, the ability to socialize face to face. Paradoxically, your little one is probably shy and insecure with unfamiliar people and in new situations and has become very attached to you. The next year will bring changes just as amazing as your baby, now a toddler, continues on this wondrous developmental journey.

At 12 months, your baby's stomach can hold approximately the volume of a grapefruit. Although the human brain experiences its greatest growth in the first year, it continues to grow and change into adulthood.