A novel phenomenological approach to the microdomain structure formati
on or phase transformation in two-dimensional cooperative systems is p
roposed. The theory offered states that a new structure consists of pi
eces of islands, microdomains, germs, etc. and deals with modeling of
the pattern formation process with increase of area of a new structure
or phase. The kinetics of the process is studied. Probabilistic chara
cteristics are obtained and first three moments of the process are ana
lyzed.