  A cell's behavior is a consequence of the complex interactions between its
numerous constituents, such as DNA, RNA, proteins and small molecules. Cells
use signaling pathways and regulatory mechanisms to coordinate multiple
processes, allowing them to respond to and adapt to an ever-changing
environment. The large number of components, the degree of interconnectivity
and the complex control of cellular networks are becoming evident in the
integrated genomic and proteomic analyses that are emerging. It is increasingly
recognized that the understanding of properties that arise from whole-cell
function require integrated, theoretical descriptions of the relationships
between different cellular components. Recent theoretical advances allow us to
describe cellular network structure with graph concepts, and have revealed
organizational features shared with numerous non-biological networks. How do we
quantitatively describe a network of hundreds or thousands of interacting
components? Does the observed topology of cellular networks give us clues about
their evolution? How does cellular networks' organization influence their
function and dynamical responses? This article will review the recent advances
in addressing these questions.
