The butterfly effect!
The butterfly effect is a popular phenomenon that has remained out of the scope for science. The very definition of the butterfly effect seems to be debatable. Tiny changes in the initial condition of a large non-linear system like the functioning of the brain or the ecosystem can cause huge changes in the system itself. Example, the flapping of the wings of the butterfly can cause tornado in some other place. Given the extremely high complexity of the problem, the study of the dynamics of such a change to happen has remained out of the scope of science.