Microtubules first
Items can be routed with microtubules and pickers. Pickers move items from and to buildings, while kickers force item direction.
Supply
Supply starts with microtubules and pickers, then grows into extracellular vessels, arteries, veins and capillaries.
Circulation later
Arteries transport blood from cardiac pumps around extracellular tissues, and capillaries exchange contents with outside.
Membrane exchange
Membrane transporters move specific items across membranes; cotransporters can move two items together or exchange them.