1. An imaging system ( 100 ) for enhancing microscopic images of unstained cells, the imaging system ( 100 ) comprising: a light source ( 102 ) for producing light ( 120 a ); a sample holder ( 109 ) for containing cells to be imaged; a condenser ( 104 ) for focussing the light ( 120 b ) at a focal plane within the sample holder ( 109 ) on the cells to be imaged; a translation mechanism for moving the focal plane of the light ( 120 b ) relative to the sample holder ( 109 ); and a detector system ( 112 ) configured to acquire a plurality of images at respective focal planes within the sample holder ( 109 ) and to process the plurality of images to provide an enhanced processed image (U r ) by analysing both dark and bright features of the plurality of images.