In this talk, we present a mechanism for the role of environment in stabilizing or controlling the dynamics of a complex system. We consider a situation in which the system and the environment are in a feedback loop and their mutual influence leads to regulation of collective dynamics of connected systems. As a specific case, we consider the disruption to neuronal dynamics caused by interaction with an environment or external agency or medium. We also discuss how excitation waves produced on a lattice of neurons due to localized abnormal neurons, can be suppressed by interaction with a collection of passive cells. The mechanism, however, is quite general and can model several other situations like spreading of Dengue by mosquitoes.