Millimeter-sized neural building blocks for 3D heterogeneous neural network assembly.

A millimeter-sized neural building block (NBB) shows high versatility to form a 3D heterogeneous neural component. A millimeter-sized 3D neural network between heterogeneous neural tissues is established, and an efficient technique is then developed to observe the spatiotemporal metrological changes of single neuron in the NBB. This technique allows the visualization of axonal extension, dendritic branching, and morphological changes of presynaptic components and synapses in real time.