3D mesostructures with a height of up to 1 mm and micrometer feature size are fabricated employing a writing speed of 1 cm s(-1) via direct laser writing utilizing a novel functional photoresist based on the radical coupling reaction of thiols and alkynes. The refractive index of the resist-consisting of a tetrafunctional thiol, a tetrafunctional alkyne and a photoinitiator-is tailored to be compatible with the employed high numerical aperture (NA) objective lens, thus enabling a Dip-in confi guration. Mesostructures are characterized by scanning electron microscopy, optical photography, and nondestructive 3D time-of-fl ight secondary ion mass spectrometry. Woodpile photonic crystals are fabricated as benchmark structures in order to investigate the axial resolution. Verifi cation of the chemical fabrication mechanism is achieved via transmission Fourier transform infrared (FTIR) spectroscopy of fabricated cuboid structures by monitoring the decrease of corresponding thiol and alkyne absorption peaks. Postmodifi cation reactions, namely the thiol-Michael addition and the copper-catalyzed azide alkyne cycloaddition, are conducted employing residual thiols and alkynes throughout the cuboid structures. Successful dual and orthogonal modifi cation throughout the structure and on the surface is achieved and verifi ed utilizing transmission FTIR spectroscopy and time-of-fl ight secondary ion mass spectrometry.