Recently we have discovered and optimized the first practical synthesis of non-fused pyrrolo[3,2-b]pyrroles via domino reaction of aldehydes, primary amines, and butane-2,3-dione [1]. Six bonds are formed in heretofore unknown tandem process, which gives rise to substituted pyrrolo[3,2-b]pyrroles – the ‘missing link’ on the map of aromatic heterocycles. Unparalleled simplicity and versatility of this one-pot reaction, non-chromatographic purification and superb optical properties (including strong violet, blue or green fluorescence both in solution as well as in the solid state), brought these molecules from virtual non-existence to the intensively investigated area functional π-systems. The parent 1,4-dihydro-pyrrolo[3,2-b]pyrroles served as building block to construct various π-expanded analogs including diindolo[2,3-b:2',3'-f]pyrrolo[3,2-b]pyrroles [2-4]. These compounds constitute the most electron-rich ladder-type heteroacenes known to date - HOMO was located at ~(−4.6) eV. Strongly fluorescent diindolo[2,3-b:2',3'-f]pyrrolo[3,2-b]pyrroles represent the longest ladder-type heteroacenes and the only existing compounds bearing the 1,4,5,8-tetrahydropyrrolo[3,2-b]pyrrolo[2',3':4,5]pyrrolo[2,3-d]pyrrole core. [1] M. Krzeszewski, B. Thorsted, J. Brewer, D. T. Gryko, J. Org. Chem., 2014, 79, 3119. [2] B. Dereka, A. Rosspeintner, M. Krzeszewski, D. T. Gryko, E. Vauthey, Angew. Chem. Int. Ed. 2016, 55, 15624. [3] M. Krzeszewski, D. Gryko, D. T. Gryko, Acc. Chem. Res., 2017, 50, 2334. [4] S. Mishra, M. Krzeszewski, C. A. Pignedoli, P. Ruffieux, R. Fasel, D. T. Gryko, Nat. Commun. 2018, 1714.