Structures 3D printed inside living human cells that has one-fifth width of a human hair

Slovenian researchers have successfully 3D printed tiny polymer structures directly inside living human cells using laser-based two-photon polymerization, overcoming the challenge of placing solid objects within the extremely small 20-micrometer cellular space. The team injected photoresist material through ultra-fine needles and used ultrafast lasers to create various microstructures, including 10-micrometer elephants and hollow spheres, with about 55 percent of cells surviving the process after 24 hours.