Mark Cavolowsky, Adam Bry and I were on a team that created a basic model of the cell membrane. The simulated cells grow and divide, suspended in a simulated fluid.
Each cell consists of a loop of masses and springs. The masses interact with the fluid model, which is just a simple diffusion grid.
The simulation allows the user to change the concentration of the fluid by clicking on an area with the mouse. The varying concentrations cause interesting effects. Cells can even shrink or burst if the concentration is too extreme, which is what happens with real cells.
With only a couple cells, the simulation is actually fast enough to be interactive. But if left running, the exponential growth of the cells puts tremendous strain on the CPU. It took 20 minutes to compute the final frame.
The simulation was done using the PyGame package for Python.