  The outstanding problem of controlling complex networks is relevant to many
areas of science and engineering, and has the potential to generate
technological breakthroughs as well. We address the physically important issue
of the energy required for achieving control by deriving and validating scaling
laws for the lower and upper energy bounds. These bounds represent a reasonable
estimate of the energy cost associated with control, and provide a step forward
from the current research on controllability toward ultimate control of complex
networked dynamical systems.
