In nature, proteins fulfill manifold different functions and are crucial as, for example, enzymes or templates for the controlled formation of structural components such as bones. The Wennemers group is intrigued by the question of whether also peptides with significantly lower molecular weights than proteins can fulfill functions for which nature evolved large macromolecules. Specifically, we ask whether peptides can serve as effective asymmetric catalysts, synthetic collagen-based materials, or imaging and targeting vectors. The lecture will focus on stereoselective peptide catalysts of the general type H-Pro-Pro-Xaa. These peptides allow for catalysis via an enamine intermediate with loadings of as little as 0.05–1 mol% and provide synthetically versatile products from aldol and conjugate addition reactions with high stereoselectivities. The lecture will discuss the scope of the peptide-catalyzed reactions and insights into the mechanism. We will also show the importance of the conformational properties of organocatalysts and highlight how changes in the conformational properties enable tuning of the catalytic activity, stereoselectivity, and chemoselectivity.