Having a newborn can be one of the most memorable experiences for someone in their lives. It comes with joy and sometimes anxiety, rightfully so. Newborns are changing everyday. One day they could only be laying on their back and the next they could be rolling over on their own. As science has shown, newborns grow at an exponential rate between when they are born and the age of two. Below are some facts addressed in the premiere of Inside The Living Body that may help to answer some questions for the new parents out there.

• Our heart is the size of a walnut when we are born, but it is still powerful enough to pump blood through tens of thousands of miles of blood vessels.

• At birth, the heart has already been pumping in the womb for eight months. But now two potentially fatal flaws are apparent: a hole in the aorta and another in the heart. In the womb, they diverted blood away from our inactive lungs. Now that the lungs are needed, the holes seal shut.

• When we are born and for the rest of our lives, there are more bacterial cells in and on us than human cells.

• When we are newborns, the hypothalamus in the center of our brain does not yet know how to regulate temperature, but brown fat — a tissue also found in hibernating animals — insulates all of our major organs while our brain and body gradually learn how to regulate our body temperature.

• Suckling is normally a subconscious reflex. A baby has no more control over it than over the urge to breathe.

• As newborns, our sight is fuzzy and we see mostly in black and white because the cones — the cells that transmit color — are still developing. We can finally see properly when we are about 8 months old.

• At 4 weeks old, our hearing is at its prime. The ossicles located next to the eardrum inside our ears, are the tiniest bones in our body. They turn up the volume 22 times.

• We are born with underdeveloped immune systems. When a mother’s skin comes into contact with the germs on her baby’s skin, she absorbs them and creates antibodies, which are then delivered to the baby in the milk from her breast.

• At around 8 months old, a baby’s 20 “milk teeth” start to force their way out from under the gums. This painful teething process eventually enables the infant to eat solid food.

• Though we are born with a complete skeleton, much of it is cartilage. Over time, special cells called osteoblasts turn the soft cartilage into hard bone. By age 1, our growing skeleton can support our body weight, allowing us to become more mobile.

• By the time we are 1, we have tripled in size. If we kept this up, by the time we’re 4, we’d weigh almost as much as a blue whale.

• Our ears play a big role in helping us to walk. Deep inside our ears, there are three looped structures — the semicircular canals — each about the size of a dime. Filled with liquid, they help us determine balance and our direction of movement.

• By the time we are 2, we are learning, on average, 10 words a day — but we can understand about 300. Nothing else, not a trained chimpanzee or even a sophisticated computer simulation, can match the learning abilities of an average 2-year-old child.

• With increased language and intelligence comes a new phase of development: awareness of our own identity. By 2 years old, we are conscious of our individuality.