Real title is "Coffee – a ubiquitous substitute for uranyl acetate in staining of biological ultrathin sections for electron microscopy studies" but the headline limits on HN are really, really tough. I had to cut more and more and more.

From the abstract:

> The use of uranyl acetate, a staining agent successfully used for decades in electron microscopy of biological specimens, is now strictly regulated by law due to its toxicity and radioactivity. It is even banned in some laboratories. In the meantime, there are a number of substitutes on the market, none of which comes close to the very good staining results of uranyl acetate, or only partially, and some of which are also toxic. In this paper, two alternatives to uranyl acetate are presented, namely coffee, which is used in countless households, and pure chlorogenic acid, which is a component of coffee.