Cross-section through a human lens.
It is the only transparent tissue of our body and it is critical for focusing light. Embryonic lens cells possess the unique ability to activate a self-destruct program that aborts just before completion, thereby leaving empty but sustainable cells to transmit visible rays precisely from the outside world to the retinal layer.
Layers of lens cells align in parallel (top and bottom), so that light passes perpendicularly through them. Within a layer (center) adjacent cells interlock like jigsaw puzzle pieces to prevent gaps from forming when the lens changes shape during focusing; the layering and interlocking of cells enables light to pass across cell boundaries without scattering.