This article describes a method and platform for fast prototyping of monolithic 3D microstructures, capable of producing arbitrary positive, negative and suspended 3D geometries, as well as sealed spaces and aligned 3D geometries using standard photoresists and few fabrication steps. Here a microfabrication method employing a mask-less micro-projection lithography platform, which co-exists on a routine fluorescence microscope, has been refined to produce a variety of 3D microstructures with up to 5 µm spatial resolutions and 10:1 aspect ratios, as well as its integration within macroscopic areas of several millimetres with up to 30 µm spatial resolutions.