Genetic approaches to modify starch in crops have been limited by our knowledge of starch biosynthesis. Recent advances in Arabidopsis have revealed key genetic components determining the size, shape and number of granules in a plastid. This has opened the doors to new discoveries on granule initiation in crop species. In parallel, advances in genomic resources and gene editing technologies allow targeted manipulation of starch biosynthesis genes in isogenic crop backgrounds. Such technologies have been successfully deployed to alter starch composition, and can now be used to modify other starch traits. This will allow the complex relationships between starch structure and physicochemical properties to be elucidated, which will facilitate the rational manipulation of starches in crops.