This lecture delves into the molecular cues involved in neurulation, focusing on the role of Sonic Hedgehog in determining the development of the neural tube. It explains how Sonic Hedgehog polarizes the neural tube and how opposing signals contribute to precise cell positioning. Additionally, it explores the activation of dorsal signaling by BMP families and the establishment of secondary organizers in brain development, highlighting the importance of providing unique cues for the formation of specific brain regions.