This image shows the solution after its is placed in a centrifuge. You can see the distinction between the sponge cells (orange) and the density gradient (clear) used during the process. The density gradient is used to separate fungi and bacteria cells from the sponge cells. The less dense cells float to the top of the tube, and the denser cells fall to the bottom. Dr. Pomponi wants only sponge cells and will remove all other cells before culturing. Image courtesy of T. Piper, NOAA.