On light microscopes, the sample can be either dead or living. But when using an electron microscope, the sample must be dead, not living. Electron microscope samples require extensive experience, time and equipment to properly prepare the samples before they can be used. Most light microscopy methods have minimal set up requirements.
The advantage of using a light microscope over a more powerful electron microscope is in the fact that you can use a dead or living sample. The electron microscope on the other hand requires that your sample must be dead, not alive. Unlike the electron microscopes, light microscopes lets the user to see living cells in action.