The Virtual Cell (VCell) is a unique computational environment for modeling and simulation of cell biology. It has been specifically designed to be a tool for a wide range of scientists, from experiment cell biologists to theoretical biophysicists. The creation of biological or mathematical models can range from the simple, to evaluate hypotheses or to interpret experimental data, to complex multi-layered models used to probe the predicted behavior of complex, highly non-linear systems. VCell is developed by the National Resource for Cell Analysis and Modeling, supported by NIGMS.