Several years after inventing an instrument capable of both measuring a cell's direction of motion and determining which parts of the cell are shifting forward, David Soll, University of Iowa biologist and cell motion expert, just isn't satisfied with the two-dimensional tool. He and colleague Edward Voss have embarked on a project to create a viewing system that will allow scientists to look at cells in three dimensions. Soll sees a need for such an instrument because, "A living cell placed on a slide has limitations; things can only move sideways. But in the human body, cells move in three dimensions." The project is expected to take three years to complete; Soll and Voss have already written about half of the software, and the first machine is scheduled for completion in 1991. What will the new tool allow you to do? "You will be able to watch cells in 3-D...