You cannot study differences of what everyone is Soul Manifestation Review made of. From the outside everyone is the same, the basic system of the body from the inside is the same but what you believe in and how you go about that belief changes everything inside of you.
The human body is full of space; the true mass, if the space is taken out three people would fit on the head of a little pin. Consider this; 85% of your brain is water, 75% of your body is water and the blood in you consists of 90% water. Other than this, you still have your spirituality, the spark of life, you have thoughts and intelligence. If you didn't then you would just be a walking mass of meat.
Remember, you are what you believe. If you believe all the positive things in life, you will have a profound and free attitude and will enjoy what time you have here. If you are a negative person you will spend your life in turmoil. Decide what you are, and what you want to be.