The development of flower, fruit, and seed of calamansi, from initiation to commercial maturity, is described in terms of time intervals. This study provides the morphological ontology on calamansi fruit, a prerequisite for crop breeding programs. Sections of flower, fruit, and seed were stained with a 1% safranin solution and examined under a dissecting microscope. The developmental phases can be grouped into 9, 3, and 4 in floral, fruit, and seed, respectively, with distinct morphological events. The time for the flower to reach anthesis from bud formation was 17 to 23 days. The development of fruit took 78 to 84 days from anthesis to commercial maturity. The development of fruit from flower bud formation to commercial maturity took 94 to 101 days. During this period, ovule development became evident in 7 days from flower bud formation. On the 59th day, a zygotic embryo became visible. On the 73rd day, somatic embryo became distinct and endosperm tissue became gummy. On the 94 to 101st days, where the fruit reached commercial maturity, the somatic embryos occupy the whole sac and the peel became smooth and shiny. The results imply that cross-pollination can be accomplished before 17 to 23 days from flower bud formation. Immature fruit at 59 to 73 days from flower formation is an appropriate fruit-age to obtain zygote, nucellus, and endosperm tissues for breeding through plant tissue culture.