Chemistry is the art of transforming matter. Although turning lead into gold does not really work, chemists can design, select, and synthesize new compounds with exceptional properties, in particular, drugs for treating diseases. One critical aspect of drug-discovery technology is the activity-selection step, which is necessary because it is not possible to reliably predict the nature and magnitude of the molecular interaction between a drug target such as an enzyme and the drug itself. Selecting for active compounds therefore must rely on high-throughput screening, whereby a reference assay for a given activity is used to test series of compounds. The development of high-thoughput screening was a consequence of the invention of combinatorial chemistry, a technology which enabled chemists to synthesize millions rather than tens of compounds within a very short time. The essence of combinatorial synthesis was to prepare large numbers of compounds by using only a few operations, such as in the split-and-mix protocol. These methods involved in part the handling of compound mixtures, but this aspect was considered too uncertain and was set aside, and the field of combinatorial chemistry has mostly concentrated on developing parallel and solid-phase synthesis methods for single compounds. The idea of compound mixtures did not just end there but soon resurfaced in a very different context, that of supramolecular chemistry. As defined by Lehn and Whitesides, supramolecular chemistry aims at forming complex systems by the self-assembly of molecular building blocks through noncovalent interactions without outside intervention. Noncovalent self-assembly from mixtures of molecular building blocks provides a paradigm for obtaining complex supramolecules not accessible by stepwise synthesis, and the concept was also suitable for equilibrating components linked by covalent bonds. Compound mixtures were brought back to the field of drug discovery when it was shown that equilibrating mixtures of building blocks for small-molecule inhibitors such as peptides and imines in the presence of a target binding protein resulted in an enrichment of the tightest binding inhibitors. This type of equilibrating mixture was termed a dynamic combinatorial library (DCL). The dynamism of a DCL comes to play during the equilibration phase in the presence of a target ligand. However, this dynamic state is short-lived and inexorably leads to a static state of thermodynamic equilibrium. This is quite problematic because at equilibrium it is almost impossible to distinguish between similar compounds, and a small advantage of one library member over another in binding to the target results in only a proportionately small increase in its concentration. Therefore, the DCL is able to select the best library member for binding to its target only if its properties are far superior to those of the other library members. Recent mathematical models show that a single DCL member must bind the target three to four orders of magnitude better than the average to make up a sizable portion (several percent) of the DCL at equilibrium. The situation is similar with target-accelerated synthesis. Recently Kazlauskas, Gleason, and co-workers found a solution to this mixture selection problem starting from yet another area of chemistry, biocatalysis. In biocatalysis one uses enzymes for organic synthesis, in particular for their properties as mild, environmentally friendly, and highly selective catalysts. The most commonly used biocatalytic step is the kinetic resolution of racemates, whereby an enzyme converts one enantiomer (A) of a racemic substrate (A,B) preferentially into a new product (P) while leaving the other (B) untouched (Scheme 1). The mathematical treatment of kinetic resolution as described by Kagan and Fiaud shows a surprising property: even if the enzyme is not completely selective for one of the enantiomers, the reaction leaves the unreacted enantiomer of the substrate with an optical purity higher than the intrinsic selectivity of the enzyme, that is, R@ S (Figure 1). This higher degree of purity comes at a cost, which is that the yield of the pure unreacted substrate is less than the theoretical maximum of 50%.