can I gain height after 16???

Aruna, the primary factor that influences a human's height is his/her genetic structure. There might be other factors that also help in height of a person like nutrition, hormones, activity levels and underlying medical conditions. But mostly it is genetic structure that plays a role. DNA plays  a major role say upto 80% of the person's height is responsible by the DNA. People usually grow until 18 years but then there are environmental factors as well that are included. The changes in the growth plates of long bones of their arms and legs cause the human body grow. This is usually the growth spurt. The last area to grow in a human body is the Spine. But once the bones ossify, more or less, the growth becomes lesser. While you cannot control height influencing factors, what one can do is to nurture the factors that initiate height. Nutrition is one thing you can influence and vitamins, minerals, good sleep and enough physical exercise can help you increase your height.