Since the first discovery of conducting polymers in 1970s, functional π-systems such as oligomers, polymers, dendrimers and polycyclic aromatics have received intense scientific and industrial interest due to their tunable optical and electronic properties. Functional π-systems can find many practical applications for such as flexible electronic devices (e.g. organic field effect transistor (OFET), organic light-emitting diode (OLED)), clean energy (e.g., bulk heterojunction solar cells, dye-sensitized solar cells, batteries and capacitors), display technology (e.g. electrochromic display), sensing (chemical sensor and biosensor) and dyestuff industry. Significant progress on functional π-systems has been achieved in recent years and it makes the commercial applications of these materials possible in coming years. So this special issue will focus on the recent progress on the molecular design and material synthesis of some new functional π-systems. Among various materials for OLEDs, stable blue light-emitting materials are especially important for a full color RGB display. Professor Grimsdale provides a review on the synthesis and OLED applications of a type of phenylene-based conjugated polymers. A review from Dr. Chen is focused blue-emitting materials based on small molecules and oligomers. Besides fluorescent materials, electro-phosphorescent polymers have recently attracted intensive interest for high-efficiency OLEDs and Professor Pei at ULCA provides a review on this topic. Professor Tang gives a review on a special type of luminescent materials which show unusual aggregation-induced emission (AIE) phenomenon. This kind of materials has promising applications for OLEDs, chemical sensors and biological probes. Professor Huang give a review on another special type of semiconductors based on spirocyclic aromatic hydrocarbons which can serve as amorphous semiconductors with high glassy transition temperatures. Organic semiconductors with high charge carrier mobilities are highly important for OFET and solar cell applications. Among various organic semiconductors, thiophene-based materials usually exhibit good performance and thus Professor Liu gives a review on the synthesis and device applications of polythiophene-based semiconductors. In addition, oligoacenes are also key building blocks for the construction of efficient semiconductors for electronic devices and Dr. Chi provides a comprehensive review on the synthetic chemistry of oligoacenes and heteroacenes. Organic near infrared (NIR) dyes have a lot of applications such as for laser protection, solar cells, bioimaging and nonlinear optics. The guest editor Dr. Wu contributes a review on the synthetic chemistry of soluble and stable NIR dyes based on polycyclic aromatics. Together these contributions provide a timely update on the current chemistry of functional π-systems.