Primordium

A primordium (/praɪˈmɔːrdiːəm/; plural: primordia) in embryology, is defined as an organ or tissue in its earliest recognizable stage of development. Cells of the primordium are called primordial cells. A primordium is the simplest set of cells capable of triggering growth of the would-be organ and the initial foundation from which an organ is able to grow. In flowering plants, a floral primordia gives rise to flowering plants.