Now, clearly our organs do grow with our bodies. No, the organs that are currently keeping you alive are not the same size as when you were born. In fact, two organs we consciously use every day, our ears and nose, continue to grow until the day we die. The human body is home to 11 organ systems that are powered by around 80 organs. While each organ does grow at its own rate until it is fully developed, how each organ develops varies on an organ-to-organ basis.

Let’s start off with two of our most important organs: the brain and the heart. Our brain at birth is 25 percent of the size it will reach. However, by the age of 2 our brain is 80 percent of its adult size. Needless to say, brains grow fast. Our heart, on the other hand, is generally the size of our fist at that particular point in our life. Once we stop growing, our heart stops growing. Unless we have a condition that causes our heart to keep growing, such as high blood pressure or heart valve disease.

Why is smoking during childhood such a bad idea? Because our lungs are not fully developed until we reach our late teens or early 20s. Our liver grows to its full size at the same time as our lungs. Of course, our liver is also capable of regenerating itself, which makes liver transplants possible. Last but not least are our eyes. Although our eyes do grow after birth, the growth is minimal and stops around the time we turn 13.