A baby's immune system is not fully developed until he/she is about six months-old. In the meantime, pregnant mothers pass immunoglobulin antibodies from their bloodstream, through the placenta, and to the fetus. These antibodies are an essential part of the fetus's immune system. They identify and bind to harmful substances, such as bacteria, viruses, and fungi that enter the body. This triggers other immune cells to destroy the foreign substance.
A group of similar (accoding to function) types of cells, when comes together to perform a specific function, then it forms a tissues.
When a group of similarly working tissues come together then they form an organ.
And this relation could be written as
cell > tissue > organ
So, organ is a collection of tissues and tissues are collection of cells.
Once the substance achieved a stable octet, it no longer reacted with the chemicals.
