Recent advances in on-surface synthesis enable the creation of carbonbased nanomaterials with atomic precision, revealing novel (opto-)electronic and magnetic properties. We developed strategies for synthesizing nonbenzenoid carbon networks, including the biphenylene network, a metallic carbon allotrope with 4-6-8-membered rings [1]. Additionally, we synthesized tridecacene [2] and pentadecacene [3], the longest acenes to date, which exhibit open-shell antiferromagnetic ground states and spin-excitation features. Finally, we explore nitrogen-doped carbon nanostructures, including cycloarenes and graphene nanoribbons, showcasing their tailored properties. References: [1] Q.T. Fan et al., J.M. Gottfried, Science 372, 852-856 (2021). [2] Z. Ruan et al., J.M. Gottfried, J. Am. Chem. Soc. 146, 3700-3709 (2024). [3] Z. Ruan et al., J.M. Gottfried, J. Am. Chem. Soc. (2025), https://doi.org/10.1021/jacs.4c13296