What cellular structures can be observed with the aid of light microscopy and electron microscopy?

With a light microscope one can view the nucleus and endoplasmic reticulum, large vacuoles etc

The resolution of a light microscope is dependent on the wavelength of light that is the main beam of illumination. Light has approximately 0.4 um (UV)- 0.7um (Infrared) wavelength. Organelles smaller than about 0.5 um will be difficult to discern with a light microscope.

With an electron microscope one can view, in addition, even the ribosomes and mitochondria, chromosomes, tubules etc.

An electron microscope can discern very minute details of a cell. This is because its resolution is dependent on the very small wavelength of a beam of electrons which is approximately 0.002 um (about 10,000 times powerful than a light microscope)