Objective:To investigate the development and maturation process of intestinal organoids in neonatal mice so as to provide a new model for research on perinatal/neonatal intestinal epithelial development and related diseases.Methods:Intestinal tissue of 3-day-old C57BL/6 mice were collected and cultured for mouse intestinal organoids (MIOs) under standard conditions down to the fifth generation. The morphological changes of MIOs were observed and recorded using inverted phase contrast microscope. Real-time fluorescent quantitative polymerase chain reaction and immunofluorescence technique were used to detect the expression and location of markers of intestinal stem cells and differentiated cells of intestinal epithelium among different generations of MIOs (Selected marker genes: Lgr5 for intestinal stem cells, Tpm2 and Gja1 for fetal intestinal progenitor cells, Villin for intestinal epithelial cells, Lyz1 for Paneth cells, Muc2 for goblet cells, Chga for endocrine cells; Selected marker proteins: villin for intestinal epithelial cells, mucin 2 for goblet cells, chromaffin A for endocrine cells, lysozyme for Paneth cells). One-way analysis of variance and Bonferroni test were adopted for statistical analysis. Results:Two types of MIOs were observed, immature spheroid and mature organoids with crypt-villus structure. Spheroid was the main form in the primary culture. From primary to the second generation, the proportion of spheroids decreased from (96.61±1.36)% to (8.93±1.50)%, and so did the size ( F=12.88, P<0.001). During the second to the fifth generation, mature organoid, as the main form, increased from (91.07±1.50)% to (95.56±2.14)%. The expression of intestinal stem cell marker Lgr5 in the second generation decreased to 0.40±0.06 times of the primary one ( F=76.75, P<0.001) and then increased after this period. The expression of fetal intestinal progenitor markers Tpm2 decreased significantly during the passage (primary generation: 1.00±0.11, the fifth generation: 0.003±0.001, F=148.00, P<0.001); And the expression of Gja1 decreased from primary generation (1.00±0.14) to the second generation (0.06±0.04) ( F=197.10, P<0.001), but kept stable from the second to fifth genetation ( F=2.20, P=0.13). The expressions of gene markers of differentiated cells in intestinal epithelium, including enterocytes, goblet cells, endocrine cells, and Paneth cells, increased after the second generation (the second generation: Villin: 0.46±0.11; Muc2: 0.68±0.29; Chga: 2.53±0.16; Lyz1: 0.98±0.21; the fifth generation: Villin: 1.02±0.05; Muc2: 8.79±0.61; Chga: 4.32±0.45; Lyz1:3.81±0.36; all P<0.05). Immunofluorescence showed that villin, the intestinal epithelial cell marker protein, was distributed along the villus-side of MIOs in primary and the fifth generation culture. Mucin 2 from goblet cell and chromaffin A from endocrine cell expressed at a very low level in the primary generation, while higher in the fifth generation. In the primary culture, lysozyme from Paneth cell was evenly distributed in organoid cells, and high fluorescent dot-shaped expression was observed in the fifth generation. Conclusions:The development and maturation of immature intestinal epithelium can be simulated by continuous culture of neonatal MIOs. MIOs between the primary and second generation could be used as a research model for development of perinatal intestinal epithelium, and the second to the fifth generation as a model for neonatal intestinal diseases studies.