What is Regeneration?

Would not it be wonderful if people who have lost an arm or leg, or just a finger in an accident, could just grow a new one?
This, unfortunately, when it comes to people, it is not possible, but there are living beings in which this is possible.
The process by which living organisms restore the structure or sometimes even whole organs is called regeneration.
Among living beings regeneration is quite different.
For example, in some species of marine worms and star fish, a tiny fraction of the body can rebuild the whole organism. If there's only a small part, from it will grow a whole new body.
On the other hand, we have a kind of regeneration that occurs in our own bodies.
The surface layer of our skin is constantly wasted in the form of small pieces and replaced by other cells.
Our hair and nails are refurbished.
Even our permanent teeth are one example of regeneration.
If the organism is more complex, and the man has a very complex organism, his ability to regenerate is smaller. 
Man, like other mammals, can’t restore any organ as a whole.
But, lizards and insects can regenerate entire limbs.
Regeneration in humans is actually a repair of damage, such as broken bones, skin injuries and some types of nerve.

Regeneration is done in two ways. 

In the first case, the new tissue grows on the surface of the wound. In the other remaining parts are changed and reorganized, but does not create new material.
When new material grows (such as limbs), it grows in this way. Bud for regeneration is created on the surface of the wound. It is usually conical in shape and contains embryonic type of cell or cells such as those bearing the flesh.
These cells can develop into cells designed specifically for the construction of a new organ, they grow, and a new organ is gradually created.