Here's why:

* Size: The nucleus is a relatively large organelle within a cell, typically around 5-10 micrometers in diameter. Light microscopes have a resolution limit of about 0.2 micrometers, meaning they can distinguish objects that are at least that far apart. This is sufficient to see the nucleus clearly.

* Staining: While the nucleus is often visible in unstained cells, staining techniques can enhance visibility and detail. Common stains like hematoxylin specifically target the nucleus, making it appear dark and distinct.

While electron microscopes provide much higher resolution, they are not necessary to view the nucleus. They are used for studying extremely small structures that are beyond the resolving power of light microscopes.