Liquid crystals are substances which combine properties of both liquids and solids. To investigate the structures and slructurai defects of liquid crystals, freeze fracturing of these gel-Like substances has been performed successfully for many years. In the TEM the structures of the different types of liquid crystals have been investigated and the results confirmed the earlier investigations using polarizing light microscopy. These TEM studies extended the knowledge of structures and structural defects of this fascinating state of matter. However, freeze fractures were only carried out on liquid crystals which form around or below room temperature.

Image editing sofiware is making it possible for us as microscopists to digitally prepare our micrographs for output as working prints, figures for journals, slides, inclusion in reports, or as files for transmission via the Internet or World Wide Web. In the course of becoming familiar with various sofiware applications, I decided to have some fun colorizing and recombining some scanning electron micrographs. While this kind of frivolity has no place in the presentation of scientific data, learning to manipulate images in this silly way serves two purposes; both to bring humor into the steep learning curve, and to highlight the sobering fact that you can no longer believe what you see in print. Although we would all hate to admit it, there may be unscrupulous scientists in our midst, tempted to alter visual data to suit their needs. Having said that, let me now show you one way it can be done...!

An accurate calibration of magnification, diffraction patterns and the relative rotation between the two is critical in quantitative transmission electron microscopy (TEM). The manufacturers of TEM's supply magnification values for each image magnification step and each value of camera length for their instruments, but these values have been observed to be in error by up to 10%, These errors can occur due to variations in lenses in individual microscopes as well as through power supply variations and aging electronic components. Before attempting quantitative TEM analysis, a series of calibrations of the individual TEU should be undertaken.

Colloidal gold has been used for centuries in the preparation of stained glass for windows and fine glassware. In recent years, colloidal gold particles have become a useful tool in microscopy for staining tissues and sections. Colloidal gold particles are especially useful for biological electron microscopy, Some of the reasons why are listed below.

1. * Homogeneous preparations of particles varying in size from 3μm to 20μm can be easily prepared.

2. * Colloidal gold suspensions are inexpensive to prepare. Most proteins can be easily coupled to colloidal gold particles.

3. * Most proteins can be easily coupled to colloidal gold particles.

4. * Proteins coupled to gold particles do not appear to lose their biological activity.

5. * The colloidal gold particles can be easily seen in the electron microscope.

6. * Colloidal gold does not naturally occur in biological material. Therefore, if you see it, it is because you put it there.

7. * Colloidal gold probes can be used for light microscopy, The larger gold particles can be directly observed by the light microscope. Small particles are detected by silver enhancement or epipolarized illumination.

8. * The same probes can be used for both LM and TEM imrnunocytochemistry.

The ribosome is the protein synthetic machinery in the cell. Knowledge of the structures of ribosomal RNA (rRNA) macromolecules in situ is essential to understanding their roles in ribosome mediated protein synthesis. We are using a microanalytical technique that identifies and maps elements directly, electron spectroscopic imaging, to determine the rRNA phosphorus distributions within Escherichia coli ribosomal subunits, and to combine the two-dimensional maps into a three-dimensional elemental distribution by iterative quaternion-assisted angular reconstitution of ribosomal particles at random orientations.

As the number and variety of ceramic materials have grown so rapidly in the last few decades, ranging from silicon nitride structural ceramics to the perovskite superconductors to the ferroelectric oxides to semiconducting sensors, the number of scientific and technical issues has also grown rapidly. Many of the basic questions relate to the role the microstructures play in determining the observed physical behavior, but increasingly it is not the geometric properties of the microstructure that are of central concern but rather compositional variations and associated electrical characteristics.

I would not, repeat *not*, recommend fixing any virus sample before attaching it to the grid. If you are concerned with pathogenicity, you can fix it after allowing it to adhere to the grid, then wash with water and stain, or you can UV irradiate both sides of the grid after staining. For speed in reporting clinical results (we do almost 1000/year), we look at negative stains of potentially infectious material without fixing by keeping a separate specimen holder for "dirty" grids and another for nonpathogenic material such as sections. The grids are then UV irradiated before storage,

The world of forensic microscopy is complex and challenging. There is a never-ending variety of requested examinations and consequently, the analyst is often asked to work in an area of little familiarity. Adding to the challenge is the inherent problem of having no exact information as to the condition of the sample prior to the crime. The forensic microscopist is expected to have mastered proficiency in polarized light microscopy in order to identify fibers, minerals, insect parts, woods, metals, biological fluids, pollution particles, microchemical techniques, paints, pigments, pollens, drugs, explosives, diatoms, safe insulation, etc. and to compare samples of all the these plus hairs, glass, etc., etc.

I had recently been involved in a computer group discussion about the Warth in-Starry stain. No one seems to like to do it, except me. Here is a procedure that my histology laboratory (The Toledo Hospital, Toledo, Ohio) received from Lee Luna, who was a consultant to our laboratory, just before his death, Any "tips-of-the-trade" I have added.

Fluorescence microscopy has proved to be an invaluable tool for biomedical science since it is possible to visualise small quantities of labeled materials (such as intracellular ions and proteins) in both fixed and living cells, However, the conventional wide field fluorescence microscope suffers from the disadvantage that objects outside the focal plane also fluoresce (in response to the excitation light) and this leads to a marked loss of contrast for objects in the focal plane, This is especially a problem when the fluorescent probe is distributed throughout the thickness of the cell and the cell is thicker than about 1 µm. The confocal microscope overcomes this problem by illuminating the preparation with a point source of excitation light and limiting the collection of light with a pinhole that is confocal with the illumination source.

These are perhaps the most fundamental interactions of light with matter, since they must often precede some of the other interactions described later. A good account of most of these will be found in the book by Slayter (1970). When light falls upon an object some of it will be reflected, some of it absorbed, and the remainder will be transmitted, phenomena which are familiar from everyday life, Most of the objects we observe are seen by the light that they reflect towards the eye, and their different surface appearances depend on the nature of this reflection. Some objects are transparent, enabling us to observe them by virtue of the light that they transmit - wine in a glass, church windows and colour transparencies are obvious examples.

Microscopists in today's laboratories face multiple challenges. Many must examine specimens according to legal, governmental or grant-specific requirements. Protocol requires that the specimens be documented by conventional photography, electronic imaging techniques, or both. Because of the thousands of specimens examined, operators work under conditions of potential physical strain for hours at a time. And the material they examine requires that they have expertise with large and complex imaging instruments.

The accuracy and precision of the quantitative measurements made with various types of scanning probe microscopes (SPMs) can be limited by instrumentation error. The piezoelectric scanners that are utilized in SPMs control either the motion of the cantilever probe with respect to a stationary sample or the motion of the sample with respect to a stationary probe. While these scanners offer many advantageous characteristics that are critical to the performance of SPMs, they also exhibit several behaviors, e.g., hysteresis and creep, that introduce uncertainties in measurements. Also, the nonlinearities associated with the photodiode used in the optical lever detection system can detract from the accuracy of measurements

The following is a technique for analyzing the area underneath a GaAs integrated circuit or discrete device which may aid in failure analysis. This procedure has been used in the past by the microelectronics community, and it is reviewed here for GaAs monolithic microwave integrated circuits (MMICs) and discrete devices. Because it is a destructive method, we use it in our lab after all other testing is completed. The substrate thickness of the GaAs is ∼4 mils (25 μm).