Accrete

To build, gather together (v.)

One ant brings a piece of sand
and lays it down
and then other ants do this
and then they live in the pile together.

One cell becomes cancerous
and begins to cry proteins
and then other cells come to it
and then they all cry proteins together.

One family finds a spot on a river
and another comes to trade with them
and then other families trade there, too
and then they make a city on the river together.