No-one knows who first invented the microscope but there have been key stages in their development:
Throughout their development the magnification of light microscopes has increased, but very high magnifications are not possible. The maximum magnification with a light microscope is around ×1500 to ×2000.
The magnification of a microscope is not the only factor that's important when viewing cells. The detail that can be seen is also important.
The ability to see greater detail in an image depends on the resolution or resolving power. This is the ability to see two points as two points, rather than merged into one.
Think about a digital photo. It can be enlarged but over a certain size, you won’t be able to see any more detail. It will just become blurry.
The resolution of a light microscope is around 0.2 μm, or 200 nm. This means that it cannot distinguish two points closer than 200 nm. One nm, or nanometre, is one billionth of a metre. This is written as:
m, or in standard form as 1 × 10-9 m.
Electron microscopes use a beam of electrons instead of light rays.
There are two types of electron microscope:
TEMs have a maximum magnification of around ×1,000,000, but images can be enlarged beyond that photographically. The limit of resolution of the transmission electron microscope is now less than 1 nm.
The TEM has revealed structures in cells that are not visible with the light microscope. We can now study cells in much finer detail.