If we're going to really take care of our hair & ensure how we'll get to our maximum length, we must first understand it & understand how it grows.
It's important to know that our hair is mainly made up of protein; this protein is called keratin. Hair is also made up of moisture and other minerals. This visible part of your hair (the part we comb & style) is called the hair shaft. The hair shaft consist of dead tissue; the part of your hair that is not made up of dead tissue, is the root. Typically, we have to take care of the hair shaft to stop premature breakage, but we feed the root to ensure our hair continues to grow & grow healthily.
Your hair strands have three layers: the cuticle (the outer layer), followed by the cortex (which gives hair it's strength & elasticity) and the medulla (the center which consists of keratin cells). The real purpose of the medulla is not quite understood, however, specialists believe that it is responsible for carrying nutrients through the strand. They say, this may explain why hair is one of the first to be affective if you get ill.
You'll learn that sealing your cuticle is very important in protection the health of your hair strands. The images below show a perfect strand, the outer green lines show a sealed & perfect cuticle. The second image reflects a damaged & frayed hair strand. Most times damaged by harsh environmental conditions and/or abuse of heat.
One reason you rinse with cool water is to seal your cuticle after you have cleansed & condition. A lot of conditioners use silicones to help with this process. However, be aware of the various silicones... not all are good for your hair.
A perfectly healthy strand of hair ----------------------------------------->
A damaged strand of hair