10
History of the Microscope
During the late Middle Ages (around
A
.
D
. 1200 to 1450), the growing demand for eyeglasses led to
experimentation with lenses and making small things appear larger. As a result of this
experimentation, the first microscope was created (probably in Holland in the late 16th century—the
Dutch were masters at the craft of magnification).
The first microscopes were operated with only one lens—then the compound microscope was
invented in the 1590s, which used two or more lenses to magnify objects even more. Among the most
famous people to use a compound microscope was Robert Hooke of England. During the 1600s,
Hooke observed and recorded the miniscule parts of nature previously unexplored, such as the
intricacies of feathers, insects, and even mold. Furthermore, Hooke introduced the concept of cells—
the smallest independently functioning part of an organism.
Today scientists use microscopes to aid in the world of medicine, help build better and stronger
materials for everyday use, and even discover hidden mysteries about ancient cultures and
environments.
One of the most powerful scientific instruments in existence is called the scanning electron
microscope (SEM). Instead of magnifying objects using lenses, like your microscope, the SEM
focuses a beam of invisible particles called electrons on the object, and collects the electrons as they
bounce back. These electrons are then turned into a black-and-white image on a television screen.
SEMs can magnify some small objects as many as 100,000 times—that’s about 50 times more
powerful than the strongest ordinary compound microscope.
Cells
One subject that’s easy to observe with your microscope is a cell. Both plants and animals have cells.
Plant cells (which Robert Hooke identified) have structured walls, and basically serve as mini–food
factories. Photosynthesis takes place inside the plat cell. Photosynthesis is the conversion of solar
energy into chemical energy (or the production of oxygen and glucose from water and carbon
dioxide).
Unlike plant cells, animal cells have a permeable membrane (instead of rigid, structured walls). This
permeable membrane—through which certain things can pass—encases a number of even smaller
specialized components called organelles. An animal’s body (including yours) is entirely made up of
these cells. They range in size and shape, depending on their function and location. Even the cell’s
life span varies from type to type—heart muscle cells, cartilage cells (the soft tissue connecting your
bones at the joints), and most neurons (brain cells) can never divide, regenerate, or be replaced. On
the other hand, liver cells are replaced about every 500 days, cells in your stomach lining about every
two days, and skin cells about every one to 34 days.
Check this out!
Try taking a toothpick and gently swiping the inside of your cheek. Then take those
cells you’ve gathered on the toothpick and make a slide for your microscope. (See “How to make your
own prepared slides” on page 6.) What do you see when you observe the slide under magnification?
Now look at the prepared slides included with your microscope. Can you see the rigid walls that plant
cells are known for?
