The first microscope magnified the object ten times its actual size. They consisted of a tube with a plate for the object at one end and, at the other, a lens that magnified the object. In 1609 Galileo worked with lenses and created a more advanced instrument with a focusing device. Anton van Leeuwenhoek taught himself the methods of polishing tiny lenses of extreme curvature which provided the best magnification of the time up to 270 diameters. This led to the construction of his microscopes and his discoveries. He was also the first to see and explain yeast plants, bacteria, life in a drop of water, and the circulation of blood cells in capillaries. In his life, he used his microscope to make many discoveries about living and non-living things. Robert Hooke, who came after Leeuwenhoek, improved his findings by using his copy of the microscope. In the 19th century, Charles A. Spencer built a microscope that provided magnifications up to 1250 in diameter with lights. He also founded an industry that created microscopes (Bells, History of Microscope, About.com). An optical microscope cannot show objects that are smaller than half the wavelength of light. As a result, electron microscopes were invented in the 1930s by the Germans Maz Knoll and Ernst Ruska. For this invention they won the Nobel Prize in Physics in 1986. The way this working microscope worked was to accelerate electrons in a vacuum until their wavelength became very short, only one hundred thousandth that of light white. Fast-moving electron beams are focused on the cell and absorbed or scattered by parts of the cell to form an image. Electron microscopes can magnify objects as small as the diameter of an atom. Unfortunately there is the disadvantage that... half of the card... ...is raised, which, depending on the sample, takes a long time. The advantages are that you can see fresh, live specimens unlike the permanent chute. Permanent slides are long-lasting and are made with a special liquid and use different coverslips. They are usually brought from scientific laboratories and other places. The two most used slides are flat and concave. Flat slides are rectangular with 90 degree corners. they must handle them with care to avoid small cuts to the fingers. Concave slides contain a surface depression for liquid and larger specimens. These slides can be used without a cover, but care must be taken not to come into contact with the lenses. Coverslips are used to cover the sample and keep it in place. The coverslip is square, thin and transparent. They are available in two sizes identified as number 1 and 2. The number 1 cover is 0.13-0.17 mm thick and the number 2 covers are 0.17-0.25 mm.