If you just need to look at different cells, you will use a light microscope, but higher magnification. However, when you need to study and visualize any organelle, you must use an Electron microscope, because it will give you the level of magnification needed.
One of the disadvantages of using an Electron microscope is that a cell must be fixed, so you cannot study life processes.
In order to visualize a life process, one uses a Fluorescent microscope.
Hope this helps.