The development of the microscope allowed scientists to make new insights into the body and disease.
It’s not clear who invented the first microscope, but the Dutch spectacle maker Zacharias Janssen (b.1585) is credited with making one of the earliest compound microscopes (ones that used two lenses) around 1600. The earliest microscopes could magnify an object up to 20 or 30 times its normal size.
In the 1660s, another Dutchman, Antonie van Leeuwenhoek (1632-1723) made microscopes by grinding his own lenses. His simple microscopes were more like magnifying glasses, with only one lens.
But the high-quality, hand-ground lenses could magnify an object by up to 200 times.
Leeuwenhoek observed animal and plant tissue, human sperm and blood cells, minerals, fossils, and many other things that had never been seen before on a microscopic scale.
He presented his findings to the Royal Society in London, where Robert Hooke was also making remarkable discoveries with a microscope.
Hooke published the ‘Micrographia’ (1665), an astonishing collection of copper-plate illustrations of objects he had observed with his own compound microscope.
While looking at thin slices of cork, Hooke described what he saw as pores:
all perforated and porous, much like a Honey-comb, ... these pores, or cells, ... were indeed the first microscopical pores I ever saw.
He was the first person to use the term ‘cell’ to describe what would later be recognised as the building blocks of all living organisms, plant and animal.
Micrographia
Engraving of a flea from Robert Hooke's Micrographia.
Wellcome Collection, CC BY
Engraving of the structure of cork from Hooke's Micrographia.
Wellcome Collection, CC BY
Engraving from Hooke's Micrographia, 1665.
Wellcome Collection, CC BY
Engraving from Hooke's Micrographia, 1665.
Wellcome Collection, CC BYMicroscopic aberrations
Many researchers refused to use the early microscopes because they could not trust what they were seeing. Aberrations and impurities in the lenses caused distortions, which led to errors in observations.
Not much changed in basic microscope design over the next 200 years, but improvements in lens manufacture (such as the use of purer glass) helped to solve problems like colour distortion and poor image resolution. Mirrors were added to compound microscopes to add more light and improve the image.
But at the start of the 1800s century, the pioneering French pathologist Xavier Bichat, who carried out many investigations into tissue samples and organs, still refused to use a microscope.
Two main problems hindered lens manufacture: image blurring (spherical aberration) and colour separation (chromatic aberration). Around 1830, Joseph Jackson Lister, in collaboration with instrument maker William Tulley, made one of the first microscopes that corrected for both these faults.
With these two major issues resolved, the use of microscopes in science and medicine grew rapidly.
The microscope in the laboratory
From the 1830s, cells and cell theory became the focus of medical and biological research, thanks to the central role of the microscope in laboratory science. Researchers were able to describe the body at the microscopic level more consistently and with greater confidence in what they saw.
Between 1838 and 1839 two German scientists, Mathias Schleiden (1804–81) and Theodor Schwann (1810–82) proposed that cells were the building blocks for plant and animal life.
Schwann had a medical training and proposed that understanding cellular behaviour was the key to understanding the body in health and illness.
His theory was taken up by another German researcher, Rudolf Virchow (1821–1902), possibly the most influential teacher of pathology in the 1800s.
The microscope was at the centre of Virchow’s work on disease processes, he would urge his students to 'learn to see microscopically'. Much of Virchow’s work involved investigating tissue and cells in the laboratory and then relating his findings back to clinical changes in his patients.
He made use of the latest developments in microscopy such as the use of microtomes to cut very thin slices of tissue and the development of stains to highlight the parts of a cell.
Wellcome Collection (CC BY)
Image source
for Microscope slide of cancer cells stained purple and blue
The microscope in the field
Science Museum Group Collection
Arthur Hill Hassall (1817– 1894) was a British physician, and a pioneer in the use of the microscope as a tool in medicine and public health. In 1846 he published a two-volume study, ‘The Microscopic Anatomy of the Human Body in Health and Disease’, the first English textbook on the subject.
His second book, ‘A microscopical examination of the water supplied to the inhabitants of London and the suburban districts’ (1850), became an influential work in promoting the cause of water reform.
And in the early 1850s he also studied food adulteration, publishing his findings in medical journal The Lancet. The journal's campaign on food adulteration led directly to the 1860 Food Adulteration Act.
Hassall’s investigative work with the microscope showed how laboratory science could be used to gather evidence from the field about health and disease.
Types of microscope
In the 20th century, new instruments such as the electron microscope increased magnification and offered new insights into the body and disease, allowing scientists to see organisms such as viruses for the first time.
And technological innovations in digital technology improved techniques such as microsurgery, which combines surgery and microscopy to allow detailed and precise manipulations inside the body.
Leeuwenhoek's microscope
This copy of Leeuwenhoek's microscope is stamped 'Utrecht Copie'. The original dates from 1670–1675.
Science Museum Group Collection
Simple microscope
The simple microscope combines a convex lens with a holder for specimens. Magnifying between 200 and 300 times, it is essentially a magnifying glass.
Science Museum Group Collection
Compound microscope
Compound microscopes have two lenses: the second lens magnifies the image enlarged by the first lens. Modern compound microscopes can provide a magnification of 1,000 times. They are still the most commonly used general purpose microscopes, found everywhere from research labs to school biology laboratories.
Science Museum Group Collection
Confocal microscope
Unlike stereo and compound microscopes, which use regular light for image formation, the confocal microscope uses a laser light to scan samples that have been dyed. These samples are prepared on slides, which the device then converts into a magnified digital image. Operators can also create 3D images by assembling multiple scans. They are commonly used in cell biology and medical applications.
Wellcome Collection (CC BY)
Electron microscope
The EM2/1 electron microscope was made in Manchester in 1947.
Science Museum Group Collection
Scanning Electron Microscope (SEM)
The scanning electron microscope, or SEM, uses electrons rather than light for image formation. The sample is dehydrated and coated with a thin layer of a conductive material, such as gold. Samples are placed in an evacuated chamber to be scanned. The SEM produces a black-and-white digital image. SEMs are used by researchers to examine a range of specimens from insects to bones.
This image is a false-coloured scanning electron micrograph of a honeybee.
Wellcome Collection (CC BY)
Transmission Electron Microscope (TEM)
Like the scanning electron microscope, the transmission electron microscope (TEM) uses electrons to create a magnified image, and samples are scanned in a vacuum so they must be specially prepared.
This image is a transmission electron micrograph showing four views of the Herpes simplex virus, computer-coloured mauve.
Wellcome Collection (CC BY)Find out more
Books
- Paul De Kruif and F Gonzalez-Crussi, Microbe Hunters, 2002
- Lindsey Fitzharris, The Butchering Art: Joseph Lister’s Quest to Transform the Grisly World of Victorian Medicine, 2018
- Laura J Snyder, Eye of the Beholder: Johannes Vermeer, Antoni van Leeuwenhoek, and the Reinvention of Seeing, 2015
