Iris cells of the eye. Coloured Scanning Electron Micrograph (SEM) of cells of the anterior surface of the iris. The iris forms the delicate and adjustable diaphragm which surrounds the pupil. It is irregular and rough, its surface composed of fibroblast cells (blue). These cells are joined loosely by connective tissue fibres (green). Granules (green) may be pigments escaped from pigment cells (melanocytes) beneath this layer. A monocyte (orange) is the largest type of white blood cell and serves an immune function. The iris is movable, allowing light to enter the pupil. Magnification: x2,200 at 6x7cm size. x2,860 at 4x5ins