These pictures are among the best biomedical images acquired over the last year by the Wellcome Trust's Medical Photographic Library, and represent the cutting edge of research as it moves into the new millennium. They have been selected for their technical quality, the imaginative or scientific nature of their subject matter, and their visual impact.

The lenses and probes of modern microscopes reveal details of life we would not normally see, from the intricate sculpting on the surface of a human egg to the changing shapes of individual protein molecules. Coloured laser beams and fluorescent probes have enabled scientists to locate specific molecules within the cell, and to follow biochemical reactions in both space and time. With the increasing resolution and diversity of such techniques, the production of images has become a major tool in biomedical research. As well as creating striking and often exquisitely beautiful images, these technologies are providing new insights into the nature of life.