"Understanding the Light Microscope" consists of four original computer programs with an explanatory book. Author Dan Goldstein says using the programs can teach aspects of microscopy and diffraction often missed from formal courses, adding, '...what one non-mathematician has created should not be beyond the understanding of others!' The book aims to provide understanding at a level deeper than customary in existing texts and in a form accessible to microscope users, particularly biologists. It covers simple ray optics, the aberrations of 'real' (thick) lenses, polarized light, and the influence of diffraction on imaging. The book can be read alone, but appreciation of its contents is greatly enhanced when used in conjunction with the programs. D J Goldstein was a Nuffield Dominion Travelling Fellow at Oxford University and a visiting Professor in Pittsburgh. He taught at the Universities of the Witwatersrand (Johannesburg, South Africa) and Sheffield (UK) while publishing research in embryology, histology, immunology, histochemistry and microscopy. Since retiring in 1989 as Reader in Anatomy at Sheffield University, he has been an independent research worker in biomedical science. This book aids insight into microscope operation and imitations. The approach is non-mathematical, yet in-depth. It enables lecture time to be replaced by learning assignments. It includes a help function for all four programs. The programs have been tried and tested by 2nd and 3rd year biomedical undergraduates.