The concept that we are healthy if we don't show visible signs of illness has proven to be incorrect. We have heard or seen cases of people who suddenly pass away while sleeping or exercising. These people generally do not show signs of illness.

Bacteria and viruses can hibernate in a person's body up to 10 years without causing illness to that person.

These are germs that appear on the skin. We face a potential attack from these microorganisms at any time.

Virus lives in human cells and reproduce in great number to destroy our normal cells.

The human immune system is like a country's defense system. It protects the body 24 hours a day from the attack of germs, bacteria, viruses and chemical toxins.

The main lymphoid organs of the immune system consist of the bone marrow and the thymus. The peripheral lymphoid organs include the tonsils, spleen, lymph node, Peyer's patches, and appendix.

1. Defense:
The immune cells will create antibodies like bullets or bombs to kill the intruders.

2. Clearance:
The immune cells eliminate wastes and impurities including the remains of bacteria and dead cells from our body, through sweat and phlegm.

3. Repair:
The immune cells will repair the injured tissues like a cut to the finger, enabling the wound to be healed within a few days.