Fonio is an ancient West African cereal of the genus Digitaria, a fast-growing drought-hardy grass whose minuscule pale grains are among the smallest of all cultivated cereals. Cooked, the tiny kernels swell into a light, fluffy, faintly nutty couscous-like grain that is naturally gluten-free and central to the daily table across the Sahel, from Senegal and Guinea to Mali, Burkina Faso and northern Nigeria, where it is also known as acha or hungry rice.