  We report x-ray scattering studies of nanoscale structural correlations in
Nd$_{1-x}$Sr$_x$MnO$_3$ and La$_{1-x}$(Ca,Sr)$_x$MnO$_3$, $x$=0.2--0.5. We find
that the correlated regions possess a temperature-independent correlation
length of 2-3 lattice constants which is the same in all samples. The period of
the lattice modulation of the correlated regions is proportional to the Ca/Sr
doping concentration $x$. Remarkably, the lattice modulation periods of these
and several other manganites with a ferromagnetic ground state fall on the same
curve when plotted as a function of $x$. Thus, the structure of the correlated
regions in these materials appears to be determined by a single parameter, $x$.
We argue that these observations provide important clues for understanding the
Colossal Magnetoresistance phenomenon in manganites.
