  The nature of the phase diagrams of HTSC is clarified by discussing two kinds
of phase diagrams, that of the host crystalline lattice, and that of the dopant
glass. The latter is associated with changes in the electronic properties,
while the former is much more accessible to direct experimental identification,
by diffraction, of nanoscale phase separation. Careful examination of
electronic properties in both the normal and superconductive states reveals
that there are several electronic miscibility gaps in YBa2Cu3Ox and
La2-xSrxCuO4 that have been previously overlooked. Recent experiments on the
pseudogap in Bi2Sr1.6La0.4CuOy also reveal an electronic miscibility gap.
