The second generation of high temperature superconductors typified by Bi2Sr2Can−1CunO2n+4 and Tl2Ba2Can−1CunO2n+4 exhibits curious structural properties which have direct relevance to the superconducting behaviour particularly transition temperature (Tc). The present paper reports on investigations of structural properties at microlevel in Bi-bearing HTCS. We have found curious structural characteristics which manifests itself in the form of transformation fromap×ap×c to (2)1/2ap×(2)1/2ap×c through the loss of calcium atoms and the formation of five-fold modulated phase alongb through the loss of Ca and Sr atoms. We have also found the evidence of high periodicities (n=4) Bi2Sr2Ca3Cu4O12. The microstructural characteristics of HTCS showing the higherTc(R=0) ∼ 120 K exhibits unusual characteristics.