Two-dimensional (2D) polymers have been extensively investigated due to their promising applications as optoelectronic materials, molecular magnets, energy storage media, electrocatalysts, etc. The archetypal 2D material is graphene, which displays remarkable mechanical and electronic properties due to a fully conjugated π system. 9, 10 However, stoichiometric functionalization of graphene remains a towering obstacle in the path towards tunable π-conjugated 2D materials. Recently, we have succeeded in the synthesis of porphene, a graphene analog made of fully fused porphyrin rings (Figure ). Both graphene and porphene are fully conjugated, but they have two key differences. One, graphene has a hexagonal lattice while porphene is composed of roughly square porphyrin monomers. A half-filled square lattice is known to be susceptible to distortion, suggesting that the shape of the porphene unit cell may depend on the number of electrons in its π system. To draw a parallel to molecules, graphene can be thought as a periodic analog of the aromatic high-symmetry benzene, while porphene resembles antiaromatic cyclobutadiene, which adopts a lower-symmetry rectangular geometry. This was first noted by Osuka and collaborators on a 2⨯2 fragment of zinc porphene (Figure ). The second, more practically important difference between graphene and porphene is that the latter offers a straightforward avenue for tuning. Different metalloporphenes (MP) can be produced from free-base porphene by controlled reversible insertion of a metal ion, M, into the center of each macrocycle, without taking any π centers out of conjugation. Given the wide choice of metals M in different spin states and possible axial ligands X, porphene offers unprecedented opportunity for stoichiometric functionalization. Availability of bidentate ligands suggests that controlled stacking into periodic multilayers may be within reach. Since metal ions can be introduced into porphene and removed under controlled conditions, nanolithographic writing of patterns and design of circuitry for applications in electronics, spintronics, photonics, and elsewhere can be imagined. The ultimate resolution of this canvas for molecular painting is 8.4 Å, the closest distance between two metal centers in a metalloporphene.