3.1 Objectives
1. Learn to prepare wet mount slide and observe plant cells under optical microscope.
2. Identify various cell structures and organelles.

3.2 Introductions
The technique of preparing wet mount slide is used for morphologic and sub-cellular structure observation in clinic diagnosis of diseases and researches.

3.3 Principles
Plant cells are eukaryotic. They share some similar structures found in animal cells, such as plasma membrane, Golgi apparatus, endoplasmic reticulum, peroxisomes, ribosomes and nucleus. It can be also found that the plant cell has some special structures of cell wall, chloroplast and large vacuole which lack in animal cell.
Wet mount slide preparation is used in this experiment. It is one of the most complicated types of slide preparation and contains multiple steps. First, release a single drop of liquid sample in the center of the glass slide holder and then position in the liquid center with a set of tweezers carefully. Second, place the glass cover over the specimen slowly and avoid air bubbles carefully. Finally, remove the excess water around the slide cover carefully.

3.4 Apparatuses and materials
Apparatuses: optical microscope, forceps, tweezers, droppers, clean microscopic slides, cover slips.
Materials: onions, iodine, distilled water.

3.5 Procedure
1. Take a small piece of onion and peel off the membrane from the under side by the forceps.
2. Lay the membrane flat on the surface of a clean glass slide and then add one drop of distilled water onto the specimen. It is important to make sure that the membrane is absolutely flat.
3. Lower a thin glass cover slip over the slide carefully by a pin. Make sure that there is no air bubbles trapped in the slide.
4. Configure your microscope following the user's guidance, making sure the lowest power objective lens, such as 4X or 10x, is in line with the optical tube, and the microscope light is turned on.
5. Place the prepared slide onto the stage of the microscope and adjust accordingly.
6. Look from the side of the microscope, lower the tube using the coarse focus knob until the end of the objective lens is just above the cover glass. Be careful and don’t crack the glass cover.
7. Observe through the eyepiece lens and adjust the fine adjustment knob until the image comes into focus.
8. Swap the objective lens to high powered one, such as 40×lens, so that you can see the cells at higher magnification.
9. Record the cell shape and the nucleus and cell wall in each cell.
10. Stain the slide with iodine instead of distilled water.
1I. Repeat steps 1-9.

3.6 Additional precautions
Strictly follow the instructions when using the microscope so as not to damage it.
Hands and clothing can be stained by iodine dye. Be careful with it.

3.7 Additional Reading
The use of Microscopic Slide in Modern Clinical Medicine
Introduction
It is relevant to discuss the role of microscopic slides and modern slide analysis as it will be encountered throughout the medical curriculum and is often and diagnosis for the medical students when studying Cell Biology.
Biopsy and slide preparation
When a person is of sickness and suspected of having a particular illness, a biopsy of the affected tissue or other biological specimen is done to determine abnormalities and pathogens present, assisting the diagnosis and ultimately the patient's treatment.
This is conducted by a pathologist who uses specific methods, such as fine needle aspiration, smears, secretions or surgical resections of tissue, to prepare the slide from. Utmost care is maintained during the preparation of slides so as to ensure no contamination of the sample specimen. The pathologist also needs to ensure that the sample is handled in a manner that does not damage the issue or create additional irregularities which could impact the accuracy of the diagnosis.
Once issue is removed, it is prepared accordingly. The preparation will depend on the type of tissue being observed as well as taking into account the possible pathogens. The sample will be placed on a slide and stained with an agent such as hematoxylin, which stains proteins red and eosin, which stains nuclei dark blue or purple. This makes the tissue easier to see under the microscope. The pathologist can now view the sample under a optical microscope and identify any irregularities or pathogens assisting him in a treatment plan. An example of this process is where a skin sample of a mole is removed from a patient, a slide prepared, analyzed under a microscope and malignant issue identified, Depending on the cells present, the pathologist is able to determine whether the mole is malignant or benign.

Modern slide analysis techniques
Since we are in the technological age, it would be no surprise that digital slide analysis has become common place in modern medical laboratories. Previous, pathologists had to prepare the slides themselves and do the entire observation of the slide under microscope. This progressed to the point where a camera was adapted allowing the photographing of slides.
Currently, virtual microscopy makes it possible to convert glass slides into digital slides that can be digitized to a computer screen and then visualized and analyzed by any number of people. Digital slides can also be sent to specialist around the world, in a matter of seconds via E -mail.
The common glass slides are scanned with a high resolution scanner that is free of any dust or particles. Again, correct slide preparation techniques are vital as they can negatively impact the analysis. Computer software allows this image to be captured and viewed on a computer and analyzed accordingly.
More sophisticated software will start making it possible to automatically identify and diagnose certain pathogens.