Wolffia is the genus containing the world's smallest flowering plants.
Wolffia species are tiny free-floating aquatic plants commonly called watermeal. Individual plants are usually only a fraction of a millimetre long, with a simple body called a frond. They have no visible roots and can form green films on still freshwater.
Their flowers are extremely reduced and difficult to see without magnification. Despite their size, Wolffia plants are true angiosperms: they produce flowers and seeds. Their simplicity makes them easy to confuse with algae, but they are flowering plants in the duckweed family Araceae.
Wolffia is also notable as a fast-growing food research subject. Some species contain substantial protein by dry weight, although their nutritional and culinary use varies by region and species.