@anamur-- There are really many different types of microscopes and all use different techniques and serve a different purpose. For example, the Darkfield microscope will give you an image of a cell as well but you won't see anything internal. If you use an electron microscope, you will have to dye the cell to see the different parts. You can use a fluorescence microscope but it uses ultraviolet light.
The phase contrast microscope doesn't have as good resolution as an electron microscope and it doesn't let you magnify the object as well as some other microscopes. But it's definitely the best microscope for looking at a cell's internal structure and that too while it is alive. So for someone who wants to observe a cell in its natural state, this is the best microscope for it.
You can even observe a human embryo with a contrast microscope and watch the different stages it goes through, live! Can it get better than that?