Morphogenesis of rat retina was studied by light and electron microscope from day 14 of gestation to 55 days after birth. The results indicate as follows: 1. At the outer border of the neuroblastic layer at the 14th day of gestation, cells she wed active mitotic figures which result in the increases of thickness and differentiations of this layer. 2. At birth, rat retina is still in a premature state. But, it is begining to approach its adult condition in appearance till the 9th postnatal day. Particulary photosensitive cells are fully developed by the 14th postnatal day, so they are functional from now on. 3. It is observed that the pigment epithelium begins differentiation at the fetal period, but is not functional urtil birth 4. The pigment epithelium differentiates earlier than the neuroblastic layer. It is suggested that these two layers are so closely associated that the pigment epithelium takes part in the differentiations of the neuroblastic layer. In conclusion, rat retina is differentiated soon after the optic cup formation before the 14th day of gestation, but even new born rat retina is not functional, and then it has function as photoreceptors coincided with the eye opening.