Neurons in silk scaffold mimic behaviors of a real brain : 

It may look like a child’s stacking toy, but a colorful assembly of concentric layers is actually a three-dimensional model of a brain. A series of porous doughnuts, made from proteins taken from silkworm cocoons, serve as scaffolds for rat nerve cells to populate.

The neurons grew in the scaffold for weeks and, in some ways, began behaving as if they were in a real brain, scientists report August 11 in the Proceedings of the National Academy of Sciences. After a hard thump from a weight, meant to mimic a traumatic brain injury, neurons in the brain model showed signs of damage, including a burst of activity. The new model might allow scientists to better understand how brain cells respond to injuries.

For more on building brains, read SN's Tiny human almost-brains made in lab. 

                       - Source - Science origin international lab-sci678/narayanaa2000.