Pharmaceutical microsphere carrier for nanodrug particles, coloured scanning electron micrograph (SEM). Microspheres are small round particles, with diameters in the micrometre range. Manufactured from various natural and synthetic materials, they can be used as carriers of micro and nanoparticles for drug delivery. They are most often used to encapsulate the active drug. Drug release is usually achieved by diffusion through pores or by degradation of the microsphere shell. Magnification: x1260 when printed 10 centimetres wide.