An advantage of three-dimensional transmission electron microscopy is reviewed using our studies on effects of heat treatment and stretching on a variation of filler network of carbon blackiCBjin rubber vulcanizates. Volume resistivity is discussed with characteristics of the CB network structure, and the CB network is suggested to be more stable in 80 parts per one hundred rubber by weightiphrjCB-filled natural rubber vulcanizate than in 50 phr CB-filled one. The stretching for 40 phr CB-filled styrene butadiene rubber vulcanizate cured under an elongation ratio by a two-step process shows aggregations of CB under low strains and collapses of CB network under high strains.