Optical Microscopy is generally the first technique used to examine samples and/or to make comparison amongst samples. Some forms of clues may be found at this stage before making any sample preparation is performed. At this stage, we often ready to pin-point and document sampling sites or phenomenon encountered during other tests. With magnifications from 10x to 1000x, many details and features of sample may be made known and photographed at this stage.
Scanning Electron Microscope (SEM) shall be deployed whenever Optical Microscopy reach the limitation of giving proper view of the samples.