Fleshy fruits come in a range of shapes and sizes, but each fruit is derived from a single meristematic growing point, with the final size determined by the number and plane of cell divisions and cell expansion during ovary and fruit development. During domestication, fruit size has been a selection criterion for most commercial fleshy fruits, and it is an important industry requirement. Extensive molecular work in model and non‐model plants has identified key genes that regulate fruit size including cell‐cycle‐related genes, meristem‐size‐associated genes, controllers of cell division, and genes associated with cell expansion and endoreduplication. These genes operate in a strongly regulated hormonal context that is also influenced by the environment of the plant. While the interaction of all three of these contributes to the final shape and size of the fruit, much research is still needed to fully understand fruit shape and size in fruits. However, key genes are emerging as potential targets to manipulate fruit size, allowing the development of new fruit cultivars.