MODEL RELEASED. Toxicology research. Toxicologist using a microscope to study a muscle tissue sample during research. The tissue sample is seen pinned to a colourless plate (lower centre). The electro- chemical effects of organophosphate chemicals on the tissue are being investigated here, with the probe at lower right measuring the electrical changes as the chemical is applied. Organophosphates are frequently used in insecticides. Over-exposure can cause vomiting, diarrhoea and breathing difficulties. Prolonged exposure can lead to widespread neuromuscular damage. Photographed at Newcastle University, England.