Several applications of laser beams demand dynamic control over amplitude, phase and polarisation properties of the beams. In microscopy, manipulation of the properties of a laser beam results in a focal spot which may reveal wealth of information from the target. One way of achieving such dynamic control of a laser beam is using a computer controlled diffractive optical element such as a liquid crystal spatial light modulator (LCSLM). Based on the principle of holography such a technique can manipulate the beam without physically disturbing the experimental setup. This book introduces programmable diffractive optics as a simple and efficient way of generating arbitrary amplitude, phase and polarisation profiles of laser beams. Incorporation of an LCSLM based diffractive optical element in a confocal microscope, along with the relevant theory, is described and the results obtained are presented. This book will be useful for persons working in the field of microscopy, holography, adaptive optics, optical trapping, optical data storage, etc., where dynamic control over the properties of a laser beam can be interesting.