A group of German engineers at the University of Stuttgart led by Dr Timo Gissibl have developed a process for creating a functional micro-camera that is the size of a grain of sand. The triple lens optical head is only about 100 micrometres (0.1 mm or 0.004 inches) wide, and with the entire micro-camera casing only 120 micrometres wide. Currently it is capable of focusing on images as far away as 3.0 mm, and it will relay images along the attached 1.7 meter (5.6 foot) optical fiber cord. The micro lenses were 3D printed using a femtosecond two-photon direct laser writing process that is similar to stereolithography, simply at a much smaller scale. You can read more over on 3DPrint.com: https://3dprint.com/140323/3d-print-micro-camera-lens/