The Lemnoideae, commonly known as duckweeds, are the smallest, fastest-growing, and simplest of flowering plants. Duckweeds have been extensively used not only in the research of phytophysiology, phytogenetics, plant senescence, ecology and environmental test, but also in the treatment of water contamination, and the screening of herbicides. At present, duckweeds have shown great value in the bio-energy and bio-pharmaceuticals. Based on the studies of our laboratory, the recent researches in the taxology and the genomics of duckweeds were reviewed, and some important breakthroughs in the molecular level and the iopharmaceuticals were pointed out.