We have investigated nanoscaled domain configuration of Pb(Ti1-xZrx)O3 (PTZ) and (1-x)Pb(Mg1/3Nb2/3)O3- xPbTiO3 ((1-x)PMN-xPT) in the monoclinic phase around a morphotropic phase boundary (MPB) region thoroughly by means of a transmission electron microscopy (TEM), in order to clarify mechanism of the enhancement of the piezoelectric effect. Two types of domain structures with inhomogeneous configuration were found around the MPB region. One is domain structures characterized by the formation of the nanoscaled herringbone-type domain structures with the ~10 nm width inside the macroscopic-sized banded domains with the 100~200 nm width. The other is as an aggregation of nanoscaled domains with the average size of about 10 nm. An in-situ TEM observation revealed that these nanoscaled domain structures are inherent to the monoclinic phase, which should be responsible for the excellent piezoelecrtric response.