Failure of the "standard model" in accounting for the X-ray properties 
of galaxy clusters has led to an increased interest in understanding the
role of non-gravitational processes such as heating and cooling. 
Both heating-only and cooling-only models can account for the mean 
global properties of clusters.  Cooling-only models, however, predict too
high a fraction of cold gas and stars, and do not agree with recent
X-ray spectral observations.  Heating-only models cannot account for
the variations in ICM structure properties.    Both processes are
required to understand the full diversity in the structural properties
of the ICM.  Drawing upon insights from observations and 
from investigations of the combined impact of heating+cooling, we 
propose a scenario that may explain both "cool core" as well as
"non-cool" core clusters.