The method is based on tape stripping combined with DESI-MSI and strip-by-strip 3D data processing. The thickness of the horny layer is about 20 micrometer. When the whitening agent 4-methoxy potassium salicylate (4MSK) developed by Shiseido was applied to human skin, the method was able to show the process of penetration over 5 layers.

Shiseido press release, Dec 20, 2012