A persistent mystery for art historians and especially students of 20th century art might seem small at first: what kind of paint did Picasso use? But in fact it’s a very big shift–Picasso was thought to have been one of the first painters to switch from traditional oil paints to common house paint, which is quick-drying and smooth and allows for a very different style (it doesn’t show brush-marks, for example). Now, the Art Institute of Chicago and the Argonne National Laboratory teamed up and used hard x-ray nanoprobes to analyze Picasso’s paint at the molecular level.

And it turns out that, yep, Picasso did in fact use house paint. This couldn’t have really been done before now; experiments with both optical and electron microscopes were unable to detect the difference, since they aren’t capable of really delving deeply into the layers of paint. Read the full story here.