Housing has always been one of the hot social issues in Hong Kong. Most of the new communities in Hong Kong are 40-50 storey buildings, and even the government built public and private houses are more than 30 storey. This can not only save a lot of land resources, but also solve the housing needs of more people. But the density is really daunting. The per capita living area is only 15 square meters. The small size of the house and the super high density of the building make the sunshine the most needed thing. Balcony, a free space, has also become a luxury for some Hong Kong residents. This has led to a sharp rise in the incidence rate of depression. We extract the formation logic of monomer from the morphology of Bauhinia, the city flower of Hong Kong. A kind of luminescent body is designed, which can deform and present different functional states in day and night. During the day, the whole plate is unfolded. It can reflect natural light and provide better light for lower floors. At the same time, it can also absorb and store solar energy to provide energy for the light source at night. At night, the whole plate folds and curls to form a spherical light source. It can not only be used as the night scene element of the city, but also provide the road lighting at night. It is worth mentioning that the brightness of luminescent body is related to the distance between people and windows, which also helps to understand the psychological state of residents.