3.7—Microscopy magnification, resolution and staining

A light microscope focuses light through a thin specimen; staining increases contrast when transparent cell structures would otherwise blend together. Electron microscopes use electrons with a shorter wavelength and therefore resolve finer detail.

Prepare a thin, supported specimen, add a suitable stain and begin with the low-power objective. Stain choice depends on the material and question: methylene blue highlights animal nuclei, iodine reveals starch, and differential staining can separate tissue types.

A clear onion or animal-cell sample may show almost no boundaries before staining, but nuclei become distinct after a suitable dye. An electron micrograph can show organelles that a light microscope cannot resolve.

Magnification makes an image larger; resolution is the ability to distinguish nearby points. More magnification cannot recover detail that the microscope never resolved, and a stain is not a natural colour of every structure.