The brain's default network, a set of regions with decreased activity during goal-oriented tasks, has been the focus of much research and debate. Initially linked to "self-referential" mental activity, recent studies have associated it with internal narratives, autobiographical self, stimulus-independent thought, mentalizing, and self-projection. However, most research has focused on adults, and the development of this network remains unclear. This study used resting-state functional connectivity MRI (rs-fcMRI) to examine the development of the default network. It found that at early school age (7–9 years), the default regions are only sparsely functionally connected, but over development, these regions integrate into a cohesive network. The study also showed that in adults, the default network is highly integrated, while in children, it is sparsely connected. The results suggest that the default network develops over time, with functional connectivity increasing as children age. The study also highlights the importance of understanding the developmental changes in the default network, as it may relate to the maturation of cognitive functions such as episodic memory, theory of mind, and mentalizing. The findings suggest that the default network is not fully mature at early school age, but it is functional and may support some of the cognitive processes associated with it. The study also discusses the relationship between the default network and task-related networks, suggesting that they develop in parallel and may be important for cognitive control processes. The study used graph-theory methods to analyze the functional connectivity of the default network and found that it becomes more integrated with age. The results have implications for understanding the development of cognitive functions and the role of the default network in brain function.The brain's default network, a set of regions with decreased activity during goal-oriented tasks, has been the focus of much research and debate. Initially linked to "self-referential" mental activity, recent studies have associated it with internal narratives, autobiographical self, stimulus-independent thought, mentalizing, and self-projection. However, most research has focused on adults, and the development of this network remains unclear. This study used resting-state functional connectivity MRI (rs-fcMRI) to examine the development of the default network. It found that at early school age (7–9 years), the default regions are only sparsely functionally connected, but over development, these regions integrate into a cohesive network. The study also showed that in adults, the default network is highly integrated, while in children, it is sparsely connected. The results suggest that the default network develops over time, with functional connectivity increasing as children age. The study also highlights the importance of understanding the developmental changes in the default network, as it may relate to the maturation of cognitive functions such as episodic memory, theory of mind, and mentalizing. The findings suggest that the default network is not fully mature at early school age, but it is functional and may support some of the cognitive processes associated with it. The study also discusses the relationship between the default network and task-related networks, suggesting that they develop in parallel and may be important for cognitive control processes. The study used graph-theory methods to analyze the functional connectivity of the default network and found that it becomes more integrated with age. The results have implications for understanding the development of cognitive functions and the role of the default network in brain function.