  Extensive experimental results are presented on the multi-scale phase
modulation phenomena observed in colossal magnetoresistance manganites. Two key
types of phase inhomogeneities directly relevant to the colossal
magnetoresistance (CMR) are discussed. The first type involves micrometer-scale
coexistence of structurally and electronically different phases. We present
extensive experimental data for a prototypical system exhibiting such a phase
coexistence, (La,Pr)$_{5/8}$Ca$_{3/8}$MnO$_{3}$. These data reveal that
percolative transport phenomena play the key role in the metal-insulator
transition in this system, and are largely responsible for the significant
magnitude of the magnetoresistance. The phase composition of the multiphase
states is governed by both the electron correlations and the effects of
martensitic accommodation strain. The second type of an inhomogeneous state is
realized in the paramagnetic state commonly found in manganites at
high-temperatures. In this state, nanometer-scale structural correlations
associated with nanoscale charge/orbital ordered regions are observed.
Experimental investigation of numerous manganite systems indicates that these
correlations are generic in orthorhombic mixed-valent manganites, and that the
correlated regions play an essential role in the CMR effect.
