An explant is defined as any plant tissue, organ, or part that is used as the starting material in plant tissue culture. Its primary function is to regenerate a mass of dedifferentiated cells, tissues, organs, or a whole plant. Virtually any part of the plant can serve as an explant, provided it responds well to the nutrient media.

The five most commonly used explants include root or shoot apical meristems, leaves, cotyledons, hypocotyls, and immature embryos. While different plant organs respond differently to in vitro culture conditions, these specific parts are frequently selected for their ability to successfully regenerate into whole plants.