 Magnifying tools use lens combinations to bend light at an angle to increase the size of the image that's sent to the eye. The light traces the light rays back to a virtual image larger than the actual object. The more we bend the light, the larger the image appears. We use X after the number to represent the expansion factor of a microscopic image. For example, the magnifying glass we used in my backyard can double the size of an image. So it would be designated 2X. Therefore, if we divide the apparent size of the image by the magnifying power of the lens, we get the object's actual size. Evidence points to the first microscope appearing in the Netherlands in the late 1500s. We know that Galileo used them in the early 17th century. The discovery of things like blood cells and microorganisms in the late 1600s really accelerated interest and development. There are a wide variety of optical microscopes, but they all have three basic parts. A quality light source with focusing capabilities. A focal plane for the specimen. And key magnifying lenses called the objective and the eyepiece. Let's take a look at a few things we can see with the optical microscope. Thanks to Greg A. Smith, we have a fantastic microscopic look at what's in a backyard. With standard microscopes, we can see things as small as 0.2 micrometers. That's 0.2 millionths of a meter. Along with factors such as lens size and quality, the limit is hardwired due to a light effect called diffraction. Diffraction of light occurs when the light wave passes over a corner or through an opening or slit that is approximately the size of the light's wavelength. We see this in daily life all the time. For example, diffraction through clouds causes this common yet beautiful sight. A very simple demonstration of diffraction can be conducted by holding your hand in front of a light source. As your face approaches your fingers, you begin to see a series of dark lines parallel to the fingers. The parallel lines are actually diffraction patterns. To understand how this works, we need to take a look at the difference between particles and waves.