Brains are like buildings 鈥� they are built from the bottom up. The foundations are there right from the start, 鈥渃onstructed鈥� through a complex process that begins even before a child is born.

In the first 1000 days between pregnancy and age two, more than 700 new neural connections are formed every second 鈥� at no other time in someone鈥檚 life will their brain develop so rapidly.

And by the time a child is just five years old, 90% of the brain will be fully developed.

鈥淭he brain is most flexible, or 鈥榩lastic,鈥� early in life to accommodate a wide range of environments and interactions,鈥� say researchers from the Center on the Developing Child at Harvard University.

鈥淪ensory pathways like those for basic vision and hearing are the first to develop, followed by early language skills and higher cognitive functions.鈥�

That鈥檚 why proper nurturing care and stimulation is vital during the early years of a child鈥檚 life. The first year of a baby鈥檚 life is when the brain begins to understand the complexities of language 鈥� and those early experiences are the building blocks for later learning.聽

The #5for5 campaign launched last week by sa国际传媒 鈥� the children鈥檚 charity behind A World at School 鈥� focuses on the importance of early childhood development.

sa国际传媒 is calling for people to put pressure on world leaders to take urgent action to ensure all children aged zero to five have access to the five areas of nurturing care needed for a child to get the best start in life 鈥� , health, learning, and protection.

But birth isn鈥檛 the point when a child鈥檚 brain goes into developmental overdrive. That starts in the mother鈥檚 womb.

鈥淏rain development begins within a week of conception. At birth about 100 billion neurons, or brain cells, have been produced,鈥� experts from the early years organisation zerotothree.org told sa国际传媒.

鈥淭hese brain cells have not only spent time travelling to the right places in the brain 鈥� they are also are beginning to connect with one another.

sa国际传媒

鈥淒uring the prenatal period, brain cells are already busy sending and receiving messages about touch, hearing and movement. The sense of taste, smell and sensitivity to light are also beginning to develop.

鈥淲hile most of the newborn鈥檚 brain cells are formed during the prenatal period, the brain is not completely developed at birth. Much of the connecting neurons and strengthening of those connections take place after birth.

鈥淭he way brain cells connect and develop will be influenced by the newborn鈥檚 experiences with adults and their environments.鈥�

The researchers from Harvard University in the United States say the brain is most flexible in the early years 鈥� but this changes as the child gets older. After that initial burst of rapid growth, connections are reduced so that brain circuits become more efficient.

In the first year of a child鈥檚 life, sensory pathways like those for vision and hearing are the first to develop, followed by early language skills.

鈥淔rom the prenatal period through the first years of life, the brain undergoes its most rapid development and early experiences determine whether its architecture is sturdy or fragile,鈥� say the team in a paper called .

Genes are important in the development of a brain. But so too are experiences 鈥� especially the interaction between children and their parents or caregivers.

鈥淵oung children naturally reach out for interaction through babbling, facial expressions, and gestures, and adults respond with the same kind of vocalizing and gesturing back at them,鈥� say the Harvard team.

鈥淚n the absence of such responses 鈥� or if the responses are unreliable or inappropriate 鈥� the brain鈥檚 architecture does not form as expected, which can lead to disparities in learning and behaviour.鈥�

With many children living through the ongoing trauma of conflicts, disasters and abuse, the effects of 鈥渢oxic stress鈥� cannot be ignored.

It damages the developing brain, which can lead to lifelong problems in learning, behaviour, and physical and mental health.