There are such a lot of things which are not producing by human body naturally for their proper functions so due to this and many other reasons, the human body needs to eat those things that are containing such essential nutrients because these nutrients are those substances which are needed to perform important functions in human body. So we need to know that what are macro-nutrients and how many types of macro-nutrients are needed by human body.Micronutrients are basically those type of nutrients that are essential and are required by the body in the small amounts. As they are required in smaller amounts that's why they are labelled as 'Micro'. For optimal health of human body, the micronutrients are required in adequate amount because each of the micronutrient has a very specific and essential role in the human body.