The effect of noise in inducing order on various chaotically evolving
systems is reviewed, with special emphasis on systems consisting of co
upled chaotic elements. In many situations it is observed that the unc
oupled elements when driven by identical noise, show synchronization p
henomena where chaotic trajectories exponentially converge towards a s
ingle noisy trajectory, independent of the initial conditions. In a ra
ndom neural network, with infinite range coupling, chaos is suppressed
due to noise and the system evolves towards a fixed point. Spatiotemp
oral stochastic resonance phenomenon has been observed in a square arr
ay of coupled threshold devices where a temporal characteristic of the
system resonates at a given noise strength. In a chaotically evolving
coupled map lattice with the logistic map as local dynamics and drive
n by identical noise at each site, we report that the number of struct
ures (a structure is a group of neighbouring lattice sites for values
of the variable follow which the certain predefined pattern) follows a
power-law decay with the length of the structure. An interesting phen
omenon, which we call stochastic coherence, is also reported in which
the abundance and lifetimes of these structures show characteristic pe
aks at some intermediate noise strength.