Explain the term "Regeneration" as used in relation to reproduction of organisms. Describe briefly how regeneration is carried out in multicellular organisms like $Hydra$.

(N/A) Regeneration: It is the ability of an organism to give rise to a new organism or individual from its body parts.
Regeneration in $Hydra$:
$1$. When the body of $Hydra$ is cut into a number of pieces by any means, each piece contains specialized cells.
$2$. These cells proliferate and make a large number of cells.
$3$. From this mass of cells, different cells undergo changes to become various cell types and tissues, finally developing into a new organism.