The study investigates the development of the brain's default network, a set of regions characterized by decreased neural activity during goal-oriented tasks. The default network has been linked to various cognitive functions such as self-referential thinking, introspection, and mentalizing. Previous research has focused on the mature adult brain, but this study uses resting-state functional connectivity MRI (rs-fcMRI) to explore its development in children aged 7-9 years. The results show that the default network is only sparsely connected in children, with minimal functional connections between regions like the ventral mPFC, posterior cingulate, and lateral parietal cortex. However, as children grow older, these regions integrate into a more cohesive and interconnected network. The study suggests that the development of the default network may contribute to the improvement of cognitive functions such as episodic memory and mentalizing over time. The findings highlight the dynamic nature of the default network's development and its potential role in cognitive development.The study investigates the development of the brain's default network, a set of regions characterized by decreased neural activity during goal-oriented tasks. The default network has been linked to various cognitive functions such as self-referential thinking, introspection, and mentalizing. Previous research has focused on the mature adult brain, but this study uses resting-state functional connectivity MRI (rs-fcMRI) to explore its development in children aged 7-9 years. The results show that the default network is only sparsely connected in children, with minimal functional connections between regions like the ventral mPFC, posterior cingulate, and lateral parietal cortex. However, as children grow older, these regions integrate into a more cohesive and interconnected network. The study suggests that the development of the default network may contribute to the improvement of cognitive functions such as episodic memory and mentalizing over time. The findings highlight the dynamic nature of the default network's development and its potential role in cognitive development.