Ginkgo period: At the initial stage of fruit expansion, due to the rapid expansion of the fruit, the contents in the cortex of the fruit are less, the water content in the cells is larger, the leucoplast is not transformed, and chloroplasts are less formed, so it looks mainly white.

Green fruit stage: With the acceleration of the material accumulation process of young fruit, the amount of chloroplast (chlorophyll) in cortical cells increased and reached a peak, so the fruit turned green or dark green.

Red fruit stage: when the fruit expands, chloroplasts (chlorophyll) in cortical cells gradually decompose and transform, and lycopene, red carotenoids, yellow carotenoids and lutein gradually appear. Because lycopene accounts for a large proportion in tomato skin, the fruit turns red.

Softening after a long time: the reasons for softening are: first, the transpiration of water in the fruit is lost, and second, the cellular contents in the fruit are consumed by respiration. Because both of them are reduced at the same time, the cell volume is reduced and it is impossible to maintain the expanded state. Therefore, at this time, the fruit will gradually soften and shrink until it dries up or rots.