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On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.

Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.

Previous Week's Question Published: 21 February, 2007 Next Week's Question
Magnification needed to see cells varies by cell type
Question
At what magnification on a microscope can you actually see animal cells and plant cells?

Question
Plant and animal cells exist in a wide variety of shapes and sizes. There are exceptions, but cells generally range from about 10 to 100 microns in size, so they are too small to see without the aid of a microscope. Due to their varied sizes, different cells become visible at different magnifications. Some cells become visible at relatively low magnification. Onion root cells, for example, become visible around 20X magnification. Smaller cells, however, such as red blood cells, are visible around 400X magnification. Yet to really understand cells we have to look not only at their external shape and size but at their internal parts as well. Within cells are even smaller, specialized structures called organelles which researchers study so they can better understand how cells function. To see such subcellular structures like the nucleolus, mitochondria, or ribosomes, even further magnification is required.

However, further magnification is sometimes not possible since every microscope has a limit to its ability to magnify and resolve details in an image. Light microscopes are limited to a magnification of about 1000X and a resolution of about 300 nanometers. When higher magnification and greater resolution is required researchers turn to electron microscopes which can magnify hundreds of thousands of times and resolve biological structures at the nanometer scale. Viruses and ribosomes, for example, are only visible under an electron microscope. The superior resolving power of an electron microscope will also produce a clearer image than a light microscope at the same magnification.

Finally, one of the most important steps in imaging cells (or any sample) under a microscope is specimen preparation. Researchers take great care to prepare good specimens. If a sample is not prepared well even an expensive, high quality microscope will have trouble producing a good image. Samples must be very thin to enable light or electrons to pass through them and a stain is often used to improve contrast in the image.

Microscopy is a very exciting field and as instruments and techniques continue to improve whole new worlds are opening up for us to see.

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