You may be concerned that this issue features just a single paper in the Expository Research section. But not to worry—you will get your money's worth. Based on foundations laid by the eminent Austrian-born algebraist Emil Artin (1898–1962) you will be acquainted with improved designs for bread mixers and taffy pullers. Ingredients include topology, dynamical systems, linear algebra, the golden ratio, and Lego toys. The applications considered by Matthew Finn and Jean-Luc Thiffeault in their paper “Topological Optimization of Rod-Stirring Devices” go far beyond food preparation and extend to industrial dough production, and to glass manufacturing where inhomogeneities in molten glass are removed by stirring it with rods. The subject of this paper is the design of efficient devices that stir a fluid thoroughly. When the fluid motion is mainly two-dimensional, as in the case of glass, for example, one can model the fluid as a two-dimensional surface. Instead of using the Stokes equations to describe the fluid motion, the authors adopt a topological approach. They view the fluid as a punctured disk (the punctures being the stirring rods), and the rod motions as mappings of this disk. The mappings associated with efficient practical stirring protocols belong to the so-called pseudo-Anosov category and produce a fluid motion that is related to chaotic dynamical systems. Implementing a pseudo-Anosov mapping requires at least three stirring rods, which is why many taffy pullers have three stirring rods. The authors choose the topological notion of braids to describe the motion protocol of the stirring rods. Mathematical relations derived by Emil Artin identify those groups of braids that can actually be physically realized. In order to estimate how thoroughly a stirring protocol mixes up the fluid, one represents the braids as products of $2\times 2$ matrices, and then determines the spectral radius of the product. For three rods the best stirring protocol has a spectral radius equal to the golden ratio. One must be careful, though, to balance mathematical tractability with practical engineering considerations. Stirring protocols that are optimal from a mathematical point of view are not necessarily so in practice. Part of the reason is that the mathematical approach corresponds to a sequential operation of the stirring rods, while in practice one would want them to work in parallel. The authors devise a parallel motion protocol for stirring rods and present evidence for the optimality of this parallel protocol. This is a marvelous paper, easy to read, accessible, and most enjoyable. To top everything off, the authors built optimal stirring devices with 2 and with 4 stirring rods from Lego toy pieces. How cool is that?