Rules
Fillomino rules: Divide the grid into regions, such that two regions sharing an edge do not have the same size. Numbers indicate the size of the region it is located in. Regions can contain none, one, or several given numbers.
Example
Here is an example of a Fillomino grid and its solution
Solve online here
History of Fillomino
According to the WPC unofficial wiki and GMPuzzles, Fillomino appeared first in Nikoli in 1994.