Two-photon excitation provides the possibility of the activation of chemical or physical processes with high spatial resolution in 3D. Such strategy has been widely used in microfabrication of photonic crystals, polymer-based optical waveguides on integrated circuit boards, high-density 3D optical data storage and other industries requiring high precision. Since the photo-activated chemical or physical processes are confined only within the small focal volume, excellent spatial control could be obtained. Moreover, the excitation source with long wavelength offers the advantages of deeper tissue penetration and less photodamage, making 2PA especially suitable for various biological applications, such as bioimaging and in-vivo biofabrications. The development of novel two-photon absorption (2PA) active organic materials is essential to realize the desired functions. The first part of the thesis focuses on the novel 2PA photoinitiators (2PIs) used for two-photon induced photopolymerization (2PP), a versatile technique for precise 3D microfabrications. High initiation efficiency is the most important character for an efficient PI. Based on a potent lead structure 1,5-bis(4-(N,N-dibutylamino) phenyl)penta-1,4-diyn-3-one, several aromatic ketone-based 2PIs containing triple bonds and dialkylamino groups were synthesized via Sonogashira coupling reactions. 2, 7-substituted fluorenone-based PI B3FL, with the largest 2PA cross section of 440 GM at 800 nm, exhibited the broadest processing windows among the investigated PIs. The double bonds conversion of the cross-linking polymeric network and the mechanical properties of the microstructures were also evaluated by FTIR and nanoindentation measurements, respectively. Beside initiation efficiency of PIs, the ease and cost of preparation are also critical factors from practical aspect. To overcome the problem of the reported 2PIs derived from the complicated syntheses and expensive catalysts, a series of linear and cyclic benzylidene ketone-based 2PIs containing double bonds and dialkylamino groups were synthesized in one step via classical aldol condensation reactions. The results of quantum-chemical calculations and experimental tests indicated that the size of the central ring significantly affected the excited state energetics and emission quantum yields as well as the two-photon initiation efficiency. 4-methylcyclohexanone-based initiator M2CMK is far more efficient than its counterparts with a central five-membered ring. The ideal processing windows of M2CMK are as broad as those of B3FL but with much simpler synthesis. Straightforward synthesis combined with high 2PA initiation efficiency makes the novel initiator a promising candidate for commercialization. Based on the efficient core structures of cyclic benzylidene ketone, carboxylic acid sodium salts as water-borne functionalities were incorporated in order to expand the application range of 2PP to biofabrication. Those novel water-soluble 2PIs were applied to microfabrication at a writing speed as high as 100 mm/s within hydrophilic photopolymers with up to 50 wt% of water. Preliminary dark-cytotoxicity tests of the 2PIs were performed and the obtained results were compared to those of Irgacure 2959, the most commonly used photoinitiator in cell encapsulation. The second part of the thesis concerned on the novel arylazide used for multi-photon induced photografting (MPG), a powerful tool for 3D site-specific functionalization. As a proof-of-concept, commercial aromatic azide BAC-M was successfully grafted within the 3D matrix with high resolution under three-photon excitation. In order to enhance the grafting efficiency and reduce the required energies, we designed and synthesized a series of novel 2PA active fluoroaryl azides containing "push-pull" structures. Desired functionalities, such as alkene and alkyne groups, were introduced at the terminal amino groups for post-modification after two-photon photografting.