Why microscopes are useful in the study of cell biology?

Microscopes are useful because cells in biology are so so small they cannot me be seen with the naked eye. Light microscopes usually look at objects from 1cm to 1μm these include such objects as fruit fly, hair, cell and bacteria.

The difference between magnification and resolution.

Magnification is being able to make small objects look larger and resolution is being able to tell the difference between two objects from each other.