Embryologic development is a dynamic process that has been previously studied by examining static (usually chemically-fixed) specimens at different time periods and then extrapolating results by assembling a series of static images. Recently, Amy McMahon, Willy Supatto, Scott Fraser, and Angelike Stathopoulos have developed new methods to look at developmental migration patterns in real time. They used an optimized imaging approach and quantitative methods to analyze a two hour period during which gastrulation occurred in the embryos of fruitflies (Drosophila). Specifically, they characterized the complex interactions between cells of the ectoderm and mesoderm by tracking the movements of over 1,500 cells, which involved the analysis of over 100,000 cell positions for each embryo!

Taxonomy: Classification, especially in relation to its general laws or principles. (OED)

The world has far too many things in it to treat them all individually. One way we make progress is through taxonomy. We group things so as to be able to discuss them usefully and understand them. The best-known taxonomy is that of living things: we group them as mammals, reptiles, grasses, trees. We group crystals based on their symmetry: cubic, hexagonal, orthorhombic.

Grain boundaries remain one of the main outstanding problems in materials science. We understand crystals rather well, but we do not have a good science of grain boundaries yet. It would help to have a taxonomy of grain boundaries.

Few electron optical inventions have revolutionized the TEM/ STEM as profoundly as the spherical aberration (Cs) corrector has. Characterization of technologically important materials increasingly needs to be done at the atomic or even sub-atomic level. This characterization includes determination of atomic structure as well as structural chemistry. With Cs correctors, the sub-Angstrom imaging barrier has been passed, and fast atomic scale spectroscopy is possible. In addition to improvements in resolution, Cs correctors offer a number of other significant improvements and benefits.

Researchers at Georgetown University's Department of Physiology and Biophysics use negative-stiffness vibration isolators to help measure micron-level patterns of neuronal activity in the mammalian neocortex. The research is shedding new light into brain sensory and motor processing functions relating to cardiac fibrillation and epilepsy.

Isolating a laboratory's sensitive microscopy equipment against low-frequency vibration has become increasingly more vital to maintaining imaging quality and data integrity for neurobiology researches. Ever more frequently, laboratory researchers are discovering that conventional air tables and the more recent active (electronic) vibration isolation systems are not able to adequately cancel out the lower frequency perturbations derived from air conditioning systems, outside vehicular movements and ambulatory personnel. Such was the case with the Department of Physiology and Biophysics at Georgetown University Medical Center, where Professor Jian-Young Wu has been conducting research on waves of neuronal activity in the neocortex of the brain.

Much of analytical TEM is based on elemental analysis of core-shell ionizations and their role in electron energy-loss spectroscopy (EELS) and energy-dispersive X-ray spectroscopy (EDS). In these techniques, integrals of the primary or secondary ionization signals (typically over many tens of eV in energy) are used to measure and map the elemental composition of probed sample areas.

In contrast, present-day STEM EELS systems are able to reveal spectral details with resolution in the range 0.1-1.0 eV. This means that EELS provides access to electronic structure and response information that goes beyond the simple elemental composition information of the integrated core-loss signals.

In light microscopy, dark field and interference contrast are widely used for examination of transparent specimens. These methods both suffer from various limitations when photomicrographs have to be taken from fine details, especially in three-dimensional specimens requiring a large depth of field.

In common dark field illumination, the condenser either is not equipped with an aperture diaphragm, or an existing condenser diaphragm has to remain in the wide-open position. Thus, the depth of field is lower than in bright field images. Moreover, dark field imaging is associated with marginal blooming, especially in linear structures exhibiting with large differences in phase or density (e.g. cell walls, edges in crystals and other mineralogical material).

Good sample preparation is essential for acquiring successful electron backscattered diffraction (EBSD) patterns in the SEM. Mechanical polishing to obtain the required surface quality with minimal sub-surface defects and deformation that does not interfere with the quality of the diffraction data is, more often than not, an art form. Special polishing techniques, such as low force lapping fixtures, electrochemical-mechanical polishing, and vibratory polishing, have been used to minimize the sub-surface damage, but have not eliminated it. Ion polishing has been used to reduce the damage layer further. However, the commercially available ion systems suffer several drawbacks, including: 1) small area treatment (≤ 1 cm) 2) decreasing beam current density with accelerating voltages, and 3) the inability to process non-conducting samples. Barna and Pecz have shown that at 3 keV with an incident angle of 5° relative to the surface, approximately 25 nm of ion damage occurs in Si and GaAs, but at 250 eV, there is less than 1 nm of amorphization of the surface. They also showed that a glancing angle across the surface is essential for removing topographic features. The ion guns that have been available for ion polishing and ion etching of SEM samples typically cannot operate effectively below 3 keV because of the low current density.

Resonant plasmon excitations at the surface of noble metals can localize and amplify an electromagnetic field in a very small volume and are the enabling element of surface enhanced optical microscopies. Tip enhanced Raman spectroscopy (TERS) combines scanning probe microscopy (SPM) with Raman spectroscopy, taking advantage of this enhancing mechanism. So far a 20 nm lateral resolution in chemical imaging of a surface has been achieved. So far a 20 nm lateral resolution in chemical imaging of a surface has been achieved.

This article contains my personal views and was inspired by the many years of problem solving I have applied to imaging biological samples generated by microscopy. Although I come from a background in electron microscopy, I have for the last eighteen years worked exclusively in light microscopy and more recently in live cell imaging.

Here at Duke, I mentor fellow faculty, postdocs and students in finding the best ways, not only to image their experiments in the right microscope, but to anticipate the kind of data they expect to extract from their images.

Born in Iraq as Abu Ali Hasan Ibn al–Haitham, the great Arab physicist is more often known by the Latinized version of his first name, Alhazen. Although he was to eventually become a profound intellectual specializing in mathematics and optics, Alhazen's early education was geared towards religion and prepared him for a career as a minister. However, apparently unhappy in his religious pursuits, Alhazen later decided to devote himself to the study of science and became particularly intrigued by Aristotle.

It was in October of 1964 when I first used a TEM, it was at the Siemens training school run by their agent Aeon Laboratories. A service engineer (we didn't call them technicians in those days), Robin Willis ran the course, five days for just alignment and cleaning! Robin, by the way, moved to University College London, Anatomy department and became the first person to publish on the tilting of biological samples. He actually invented tomography without knowing it! He used a fish tank within which he hung the negatives of his +60 to -60 tilt series. This procedure created a three dimensional image of the thin section, again I would guess, for the first time.

It has been in the back of my mind to write this up for MT since I retired from a certain large computer company. Inasmuch as Paul's article above is a perfect lead-in, there is no time like the present. Our lab supported a semiconductor integrated circuit and a ceramic substrate manufacturing facility. We were continually required to measure circuit line widths on plan-view specimens and layer thicknesses on cross-section specimens for both semiconductor and ceramic substrate specimens and we were often asked to determine thin film grain size and ceramic raw material particle size data. A large number of measurements were required for each specimen to guarantee statistically sound data. We had image analysis software available that we used whenever we could, but often found that measuring things on a system using grey-level image analysis as input simply did not work. This is especially true for thin film grain size determination when using diffraction contrast TEM images for input.