McDougal Littell Science Cells and Heredity 

Table of Contents
Page 12

The microscope led to the discovery of cells.

Most cells are microscopic, too small to see without the aid of a microscope. A microscope is an instrument which makes an object appear bigger than it is. It took the invention of this relatively simple tool to lead to the discovery of cells. In the 1660s, Robert Hooke began using microscopes to look at all sorts of materials. Anton van Leeuwenhoek took up similar work in the 1670s. They were among the first people to describe cells.

Hooke's Drawing of Cells


Robert Hooke published this drawing of dead cork cells in 1665. The microscope he used, shown at left, has two lenses.

Robert Hooke gave the cell its name. While looking at a sample of cork, a layer of bark taken from an oak tree, he saw a group of similarly shaped compartments that looked to him like tiny empty rooms, or cells. You can see from his drawing, shown at right, how well these cells fit Hooke's description. Hooke used a microscope that magnified objects 30 times (30×). In other words, objects appeared thirty times larger than their actual size.

The bark cells Hooke saw were actually dead cells, which is why they appeared empty. Anton van Leeuwenhoek was one of the first people to describe living cells. He looked at a drop of pond water under a microscope. Imagine his surprise when he saw that a drop of water was full of living things! Using lenses that could magnify an object almost 300×, he observed tiny unicellular organisms like those shown on page 11.


How did the invention of the microscope change the study of biology?

You can understand how powerful a microscope is if you think of how big a penny would be if it were increased in size 30×. It would be a little bigger than the tire of a ten-speed bicycle. Enlarged 300×, that penny would be so big that you would need a tractortrailer to move it. Magnify your best friend 30× (supposing a height of 1.5 meters, or almost 5 ft), and your friend would appear to be 45 meters (147 ft) tall. That's almost the height of Niagara Falls. Change the magnification to 300×, and your friend would appear to be 450 meters (1470 ft) tall—taller than the Empire State Building.