This research is aimed at understanding the dynamical properties of chemically-reacting systems. Specifically, it is aimed at: (1) multi- phase reactors studying fluid flow-through trickle bed reactors, attempting to understand flow phenomena such as phase separation and channeling which can cause disfunction; (2) bioreactors, using the notion of a cell as a reactor to build a kinetic model for cholesterol uptake and usage by endothelial cells; and (3) studying cell function and pathogenesis, by drawing together work on the theoretical basis of membrane diffusion and reaction networks.