Researchers Dr. Maruša Mur, Aljaž Kavčič, Dr. Uroš Jagodič, Dr. Rok Podlipec, and Assoc. Prof. Dr. Matjaž Humar from the Department of Condensed Matter Physics at the Jožef Stefan Institute have succeeded in 3D printing microscopic structures directly inside living human cells using two advanced techniques. First, they injected a drop of biocompatible light-sensitive material into the cell. Then, using a highly focused laser beam, they selectively illuminated the printing material and polymerized it. By moving the laser beam in three dimensions, it is possible to "draw" complex structures of any shape with sub-micrometer resolution. Using this method, the team printed various structures, from geometric patterns to microlasers and even small elephants, all inside living human cells. By transforming living cells into miniature environments for 3D printing, this work pushes the boundaries of what is possible at the intersection of biology, physics, and engineering, offering a powerful new tool for exploring the workings of life from the inside out. The research was published in the prestigious journal Advanced Materials.