Complex and simple cells in the brain are fundamentally similar in their intrinsic properties, with the primary distinction arising from the synaptic inputs they receive from other neurons. This suggests that the differences between these cell types are not physical but functional, influenced by the specific roles they play in neural processing. All cells in the body share the same genetic information, but their unique characteristics result from variations in gene expression that dictate their specific functions. For instance, liver cells and brain cells activate different sets of genes to fulfill their respective roles, while maintaining essential cellular functions like sodium-potassium pumps.