[[Image:FDTD58.png|thumb|600px|EM.Tempo's Simulation Engine Settings dialog.]]
[[Image:FDTD66.png|thumb|480px|EM.Tempo's output window.]]
Once you build your physical structure in the project workspace and define an excitation source, you are ready to run an FDTD simulation. The simulation engine will run even if you have not defined any observables. Obviously, no simulation data will be generated in that case. EM.Tempo currently offers several different simulation modes as follows (click on each type to learn more about it):
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