With the development of studies in engineering dielectrics

more and more unaccepted questions arise. To provide peer reviews for these questions

we propose several important issues and thinking. The concept of nanometric dielectrics was firstly proposed by T J Lewis in 1994

and it has become the research focus of engineering dielectrics since 2003. However

from the point of view of the research results for more than 20 years

the original intention of the author and some recently-proposed nanostructured dielectrics

we believe that nanometric dielectrics should be renamed nanodielectric composites

and be redefined in accordance with low dimensional physics. The specific meaning of Lewis interface and Tanaka interface is analyzed

hard/soft interface of nano polymeric composites is proposed

new concepts of structural complexity

uncertainty and mutability are described

and the scale and physical and chemical properties of hard and soft surfaces are analyzed. New thoughts are inspired from the perspective of Einstein reductionism

emergent phenomena of P W Anderson

and scientific prediction of R P Feynmann. Constraints of existent conditions of space charge limited current（SCLC） are studied

and hierarchical levels of its self-structure

complex interface

electrode contact

concomitant electronic and ionic conductivity and other factors in polymers or their composites have serious impacts on SCLC. It is proposed that SCLC is not solely determined by carriers which are the same as injected carriers in the transition from ohmic region to high field region

i e.

electrode injection SCLC region. In particular

the contribution of ionic conductivity to the current in low and high field region is of close scrutiny when measurement conditions are determined. Therefore

the main features and distinction methods of ionic and electronic conductivity are listed. In view of pulse related space charge measurement methods

especially pulsed electroacoustic（PEA） method has been mainly adopted in the world

advantages and disadvantages of PEA

and the method for verifying the accuracy and repeatability of measurement results are proposed. According to the features of polymer structure

a pressure stimulated current（PSC） device should be built up for distinguishing space charges derived from concentration gradient of electrons

ions

and dipoles to compensate the serious shortcomings of PEA measurements.