Patient-specific in vitro models provide a powerful platform to study the cellular and molecular mechanisms underlying neurodegenerative diseases in a human-relevant context. In this presentation, I will highlight our work using brain organoids and assembloids derived from patient-specific induced pluripotent stem cells to model the human brain. These 3D systems recapitulate essential features of human brain development, cellular diversity, and interregional connectivity. I will discuss different types of human brain organoids and assembloids, covering different features like neuronal diversity, neuroinflammation, and vascularization. Together, these models represent a versatile and translationally relevant approach to bridge the gap between patient genetics and disease biology.