Polarised light micrograph of maleic acid, or cis-butenedioic acid, (H2OCCH=CHCO2H). It is an organic dibasic acid which is used for drug stabilisation and in the manufacture of fibre reinforced laminated mouldings, corrosion inhibitors and anti-scaling agents. It is also used in the production of a range of chemical products, principally fumaric acid. Magnification: x68 at 10cm wide.