Nerve connections come ready to assemble

Catering to the do-it-yourself crowd, a few companies sell the lumber, doors, windows, and everything else needed to build a home. They’ll even deliver the home-building kit to a person’s future doorstep.

Similarly, nerve cells seem to package key components of synapses—the specialized structures that allow the cells to communicate with one another—and collectively ship the material to points where these complexes take shape.