A Clear Solution

The bending of light (refraction) as it passes through one transparent substance to another is problematic for high-powered microscopes. As light passes through the sample to the air and then the lens the refraction causes blurring, reducing resolution and depth of focus. To minimise this, such microscopes use oil between the coverslip and lens. Light travels through oil and glass similarly (they have similar refraction indices) and so bends less. But what if researchers want to observe living cells at high magnification? Perhaps they want to see brain cells firing (with fluorescent calcium dye), for example, which is what’s happening in this video. Ideally, directly between the lens and brain tissue they’d have a nontoxic, transparent solution of the same refraction index as the tissue itself. SeeDB – also known as bovine serum albumin – is just that. The video shows cells without, then with SeeDB and the improvement is, well, clear.

Written by Ruth Williams

Ruth Williams

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Ruth is a freelance science journalist based in the US. She's a regular correspondent for The Scientist, and her work has appeared in The Lancet, Nature, Scientific American Mind, BBC Focus and elsewhere. Twitter @rooph

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• Video from work by Shigenori Inagaki and colleagues
• Department of Developmental Neurophysiology, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
• Video originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)
• Published in Nature Methods, March 2026