Histopahological features of rheumatoid arthritis, beginning from synovitis through deteriorating cartilage and bone to joint destruction has basically unchanged since the old days. On the other hand many inflammatory factors initiating, sustaining and/or activating inflammation such as cytokines and proteolytic enzymes, were successively detected, and followed by genetic analysis using animal models such as transgenic and knockout methods. Newly developed therapies by biological products remarkably have influenced the inflammatory these factors and genes, and seemed to modify the histopathological features. This article refers the histopathlogical features of RA in topics such as places involved in early stage, and the cellular origin, especially about the fibroblast like cells (FLS) which have been paid attention recently as key cells presenting immunological, histiocytic and fibroblastic properties, furthermore, participating the bone destruction in part as well as osteoclast in RA. We also introduce the several animal models of RA applied by many researchers for therapeutic and genetic analyses in RA.