Cargille has been serving microscopists since 1940 when it introduced the first non-drying immersion oil formula. Since then, they have continued to improve and expand their line of immersion oils to become the undisputed leaders in immersion oil technology. Oils are available in a number of different formulations and can be readily mixed to create intermediate viscosities as required. Microscopists requiring fluorescence free immersion oils will want to use either PCB-free Type DF, with the highest resolution of any fluorescence immersion oil, or PCB-free Type FF. Type FF immersion oil provides virtually no background fluorescence making it ideal for observing low levels of fluorescence. It is highly stable, non-hydroscopic, and can be substituted for all other fluorescence microscopy oils and liquids in nearly all fluorescence applications.