Twenty Years of Graphene: From Pristine to Chemically Engineered Nano-Sized Flakes.

It is a celebratory moment for graphene! This year marks the 20th anniversary of the discovery of this amazing material by Geim and Novoselov. Curiously, it coincides with the century mark of graphite's layered structure discovery. Since the discovery of graphene with the promise that its outstanding properties would change the world, society often wonders where is graphene? In this context, their discoverers said in 2005, "despite the reigning optimism about graphene-based electronics, "graphenium" microprocessors are unlikely to appear for the next 20 years". Today, possibilities for graphene are endless! It can be used in electronics, photonics, fuel cells, energy storage, artificial intelligence, biomedicine, and even cultural heritage or sports. Additionally, the electronic properties of this material have been modified in fascinating ways. Bilayer graphene sheets have been found to be superconductive when twisted at a "magic angle", leading to a new and exciting field of research known as "moiré quantum materials" or "twistronics". Additionally, small graphene fragments with nanometer sizes undergo a quantum confinement effect of electrons, affording semiconductive materials with applications in optoelectronics. Organic synthesis allows the preparation of molecules with a graphene-like pattern with total control of the shape and size, exhibiting a big catalog of chiroptical and optoelectronic properties. This Perspective shows some of the fascinating milestones raised in the field of graphene-like materials from a chemical point of view, including functionalization strategies employed to chemically modify the topology and the properties of pristine graphene as well as the rising molecular graphenes.