Optical tweezers are used in biophysics, biology, chemistry and physics for cell sorting, to measure properties of DNA and to perform spectroscopy of trapped particles. A fully interlocked optical tweezer system for single-beam trapping and manipulation of micron-size particles, the E 3100 manufactured by Elliot Scientific Ltd. of Harpenden, UK, enables their use in a Class 1 laser environment with a compact desktop unit. Using precision manual stages and high-quality imaging optics, the system can manipulate 1-µm particles with submicron accuracy.It measures 210 × 340 × 290 mm and features an internal diode laser with variable power, power display, an external laser port and backlight illumination with a variable-power cool light source. It includes a 100X oil-immersion objective with a 1.25 numerical aperture, as well as a color CCD camera with S-video out and a laser-blocking filter.The device performs cell manipulation via conjugate beam-steering optics or a precision X-Y stage, which also can be used for X-Y-Z trapping. Cell rotation of birefringent particles is possible when polarization optics are introduced in a rotation mount.The system has taken a well-known technique from the physics laboratory and made it accessible to the wider scientific community, enabling progress in the fields of bio- and nanotechnology.