A picture is worth a thousand words

Visualizing Nature at the cellulare level

Science in Your Eyes is an online image gallery showcasing the capabilities of modern imaging techniques, including examples from Confocal Fluorescence Microscopy and Atomic Force Microscopy, with emphasis on the aesthetic nature of cellular and subcellular structure. The images are taken from the world of biophysics with a special focus on cell membranes, fats, proteins and liposomes.

: Picture of Oeders troldurt. Flora Danica Proveniens Det Kongelige Bibliotek.

In the quest for understanding of the natural world, visualization of the objects under investigation has always played a central role, particularly when the entities in question are invisible to the naked eye. Images have been instrumental not only in the understanding of biological cellular systems, but also in the dissemination of information to both the scientist and the layman alike. Drawings, photography, and later video and digital imaging have represented progressive improvements in the ability of scientists to depict the natural world. The technical advances accompanying this progression have steadily allowed scientists to obtain detailed images at smaller and smaller scales, spanning a range from what is visible with the naked eye (approx. 0,2 mm) all the way down to the smallest constituents of matter - molecules and atoms (approx 0,1 nm) - the nanoscopic world.

1 nanometer (nm) = one thousandth of 1 micrometer (µm) = one millionth of 1 millimeter (mm)

: The Van Heurck No.1 model microscope, c. 1910 from W. Watson & Sons Ltd., kindly submitted by Allan Wissner.

The term microscope can be used broadly to refer to any instrument that permits visualization of objects below optical limits, i.e., at microscopic (or even submicroscopic!) levels of resolution. Different types of microscopy have constituted a central tool for understanding the structure, properties, and behavior of biological materials. Furthermore, in clinical settings microscopes have played an important role in the study of the pathology of diseases.

The optical light microscope was devised in the late 16th century and by means of a simple magnifying lens was capable of achieving magnifications of less than 10 times. After centuries of refinements in objectives and microscope design, modern light microscopes can achieve not only far greater magnifications, but by means of various contrast techniques, imaging of structures that are difficult to resolve in ordinary bright field microscopy.

More modern innovations in microscopy have involved the use of lasers and advanced optical techniques to improve resolution, for example in Confocal Microscopy and Laser scanning Microscopy. Special dyes (fluorescent molecules) have been incorporated into living and synthetic cells to selectively label specific components in the structure. The wavelength of light sets the size limit for the smallest object that can be seen with a light microscope. Therefore, for conventional microscopy it is impossible to see anything that is smaller than half the wavelength of violet light, approx. 200 nm.

However if electrons, which have an even smaller wavelength than light, are used instead to "illuminate" the object in an electron microscope, it is possible to see objects (for example, single atoms) with a resolution approaching 0,1 nm. A major breakthrough in the field of imaging of very small objects came in the eighties with the development of scanning probe techniques that allowed visualization of surfaces at the atomic level. Atomic Force Microscopy (AFM), developed in 1986, has proven to be of particular usefulness in visualizing soft, biological materials such as the lipid bilayer membrane of cells in their natural aqueous (water) environment. The resolution of the AFM allows images to be made of entities as small as a single protein or DNA-molecule (a few nm) or as large as a living cell (several thousands of nm).

Imaging the structure of a biological system on the microscopic scale provides insight into the function of the system, in turn leading to a better understanding of biological processes. The light microscope has therefore been a central tool in the field of biological and medical research for centuries. Staining, fluorescence, and radiolabeling techniques have enhanced the capabilities of microscopy to improve contrast and resolution and permitted selective visualizion of different tissue types, sub-cellular structures and special groups of molecules. In particular, fluorescence microscopy is a relatively straightforward and powerful technique, based on emission of light from fluorescent markers when excited at certain wavelengths of light. is the markers themselves can be added to the system (e.g., a cell membrane) in the lab, or in some cases are naturally present in the cell membrane.