The CKX microscopes utilize the infinity-corrected optical system for improved visibility and operability in cell checking. The CKX31 is a cost-effective inverted microscope suited to routine applications in a range of fields--from tissue culture and embryology to immunology and pharmacology. Olympus has taken this one step further with the CKX41 developing a modular design approach with the capability of a fluorescence illuminator for GFP; documentation of images with digital imaging and video monitoring. The CKX41 is routinely used for checking cell viability in petri dishes, culture flasks, and multi-well plates.