Two scientific fields have greatly benefited from the advent of 3D printing and the possibility of rapid prototyping directly in the laboratory: microfluidics and microscopy. Before the advent of 3D printing, making a microfluidic device was a cumbersome task: its steps involve making a master using soft lithography, molding and demolding PDMS (polydimethylsiloxane), alignment in case of multilayer microfluidics, and final plasma bonding of PDMS to glass, a process commonly known as replica molding. If the microfluidics did not work as predicted, the process would have been repeated multiple times to fine-tune the microfluidic parameters. This process has changed with 3D printing, where various designs can be done and printed in a few hours, speeding up the research and lowering prototyping costs. One approach is to design and print the whole microfluidic device in 3D printable plastics. Printing a single plastic block rather than having a mixed PDMS/glass device drastically increases its resistance to pressure. Moreover, the printing process can be halted during printing to add other objects inside the printed object to add new functionalities to the device, a process usually not possible in standard replica molding microfluidic fabrication. This process has been employed, for example, to add a PMMA observation window or even electrochemical detectors directly in 3D printed microfluidic devices. There is also an opensource repository of 3D models for microfluidics, not only devices themselves but also for all connections and adaptors (Figure ). Another option for using a 3D printer to fabricate microfluidic devices is to use the solubility of some 3D printing plastics to our advantage. In 2015, our group printed ABS and embedded it into PDMS. When this PDMS/ABS block is placed in acetone, ABS dissolves, leaving an open channel inside the PDMS (Figure ). This method can make a single block PDMS microfluidic device, a standard and very well characterized material in the microfluidics field, using only a standard 3D printer and 3D printing material without the need for expensive or difficult to use instruments. This method has been applied to water-soluble materials, or to manufacture interconnecting PDMS/glass microfluidic blocks. The FDM 3D printer can also be used to print a mold for PDMS replica molding fabrication. 3D printing has also been used to fabricate paper microfluidics, using the 3D printing material for directing liquids on filter paper. The second field that has greatly benefitted from 3D printing is microscopy. The possibility of fast and cheaply prototyping microscope parts has democratized the field and opened the possibility of fabricating fully 3D printed microscopes. Probably the most common 3D printed microscope is the OpenFlexure (Figure ). It uses a 3D printed stage to achieve stable movements of a few microns. Building on this kind of flexure, it is possible to 3D print a sub-100nm fiber alignment stage. This is impressive if you think that the stage is a single block of 3D-printed plastic. Another recently developme 3D printable microscope is the PUMA. The use of 3D printers has also opened the field to the fabrication of Do-It-Yourself microscopes, where various 3D printed optical blocks can be put together for different microscopy set-ups. The µCube is one of the first examples of this approach, and later the UC2 (You See Too) has improved the process, removing the need for tedious alignment of the blocks. Simply reshuffling the cubes on these set-ups can transform a brightfield microscope into a fluorescence one in a few minutes. Furthermore, 3D printing has also been used to fabricate a single-molecule microscope: the miCube. An Open Microscopy database can be found here .