Aerial surfaces of most land plants have epidermal hairs (trichomes). Both Arabidopsis thaliana trichomes and cotton fibers (seed hairs) are nonglandular hairs with unicellular structure. Here we outline the recent progress on molecular dissection of Arabidopsis trichome development,including the transcription factors regulating trichome initiation,phytohormones influencing trichome density,and the cytoskeleton formation system governing trichome morphogenesis. There is increasing evidence showing that these processes also control cotton fiber production. As several cotton fiber genes are able to rescue the Arabidopsis trichome mutants,we discuss the conservation between Arabidopsis trichome and cotton fiber development.