Right from the moment a human life is conceived, the process of development starts and it does not stop till we die. The development is a constant process that brings about a change in a being every moment, mostly in the positive direction but many a times it might cause regressive changes also.
The process of development constitutes both mental and physical development including growth of all the somatic organs of the body.
As a life is conceived, initially cell division from the fertilized ovum increases the number of cells, so there is enough number of cells to complete growth of all organs. Alongside the increase in number of cells, each cell is also gradually allotted a specific function. Initially the cells are segregated broadly and are marked to become a specific organ in the body and accordingly they take their specific place in the architecture of the human body. Later on the cells targeted for a particular organs further differentiate and form various types of cells that are necessary to a form an organ. One of the foremost organs to take shape in a developing embryo and later on the fetus is the brain, aptly emphasizing its importance in the body considering it is the control panel of the development in rest of the body. The cells destined to become brain cells or the neurons are allotted their specific function as soon as 13th day of the embryonic life. The brain then grows to accommodate around 86 (+/- 8) billions of cells at the time birth with trillions of networks between these cells.
In the first two years of life post birth, the network that are emphasized stay in the brain but those that are not used are pruned. Meanwhile child grows and experiences the gamut of stimuli form the environment and according to the stimuli perceived, it consolidates its neurological networks and so its’ function, its emotional structure, its hobbies and its personality.
Though the genetics and DNA provides the blueprint of how the human being should be, but it is the environment that by creating the stimuli, modulates how the gene would be expressed or whether that gene would be expressed or not. During the whole of prenatal period, birth and also a significant part of the first few years of the childhood, the development occurs majorly in response to the environment. How was the environment in the womb including nutrition, exposure to the chemical milieu inside the womb, even the mood and stress level of the mother when the child is developing inside her creates an environment to which the developing fetus responds and lodges a nourish or protect kind of response which further guides the gene expression, which in turns decides how well the child’d body and responses would develop. Later on during the birth, whether there was any stress to child in the form of the birth injury or any metabolic insult like kernicterus or severe jaundice determines development. Postnatally, child’s environment is majorly formed by the mother and other family members who take care of the child. And what kind of the stimuli child gets will determine his/her future perceptions, beliefs and responses and reflexes.