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<jats:title>Lewis acid catalysis tackled by tag team</jats:title> <jats:p> Molecular catalysts with two closely spaced nitrogen-hydrogen groups can act like a tweezer, activating a carbon center by latching onto a leaving group through double hydrogen bonding and then pulling it away. In the resultant ion pair, the shape of the catalyst can bias an ensuing reaction to favor just one of two possible mirror-image products. Banik <jats:italic>et al.</jats:italic> used this motif to activate a Lewis acid cocatalyst, pulling a leaving group off silicon instead of carbon (see the Perspective by Mattson). The combined pair of catalysts is more effective for reactions such as asymmetric cycloadditions that involve weaker leaving groups on carbon. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6364" page="761" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aao5894">761</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6364" page="720" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aaq0680">720</jats:related-article> </jats:p>

<jats:title>Scattered light, it is all the same</jats:title> <jats:p> Materials can vary from transparent to opaque depending on the density of scatters within the medium. As light propagates through a material, intuition might suggest that the more scatters there are, the shorter the path along which the light can propagate. Savo <jats:italic>et al.</jats:italic> confirm a recent theoretical proposal that predicts that this is not the case. They shone light through a series of samples of varying scatterer density and found that the average path length that the light traveled was independent of the sample microstructure. This finding should also be applicable to acoustics and matter waves. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6364" page="765" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aan4054">765</jats:related-article> </jats:p>