  Living systems, particularly multicellular systems, often seem hopelessly
complex. But recent studies have suggested that beneath this complexity, there
may be unifying quantitative principles that we are only now starting to
unravel. All cells interact with their environments and with other cells.
Communication among cells is a primary means for cells to interact with each
other. The complexity of these multicellular systems, due to the large numbers
of cells and the diversity of intracellular and intercellular interactions,
makes understanding multicellular systems a daunting task. To overcome this
challenge, we will likely need judicious simplifications and conceptual
frameworks that can reveal design principles that are shared among diverse
multicellular systems. Here we review some recent progress towards developing
such frameworks.
