Explain why electron microscopes have allowed scientists to understand cell structure in greater detail than light microscopes.

Electron microscopes use a beam of electrons instead of light, giving a much shorter wavelength. This allows a higher magnification and, more importantly, a higher resolution than light microscopes. Higher resolution means that structures that are only a few nanometres apart can be distinguished, so sub‑cellular organelles such as mitochondria, ribosomes and the endoplasmic reticulum can be seen separately. Consequently, electron microscopy has enabled the discovery and detailed study of these structures, which are invisible or poorly resolved with light microscopy.