Cross your eyes until the central images fuse. Some people will instantly see the fused image as a three dimensional image.  Others will have to spend time relaxing and adjusting their focus before a three dimensional image appears.

Tracings of four thalamocortical cell dendritic arbors from a circuit scale 3D electron microscopy volume of P32 mouse lateral geniculate nucleus.

Thalamocortical cells from a P32 mouse LGN.  Green cells share retinal ganglion cell input with the green seed cell (see above).  Red cells share retinal ganglion cell input with the red seed cell.   Yellow neurons are thalamocortical cells that share input with both seed cells. Given that the red and green seed cells are innervated by different kinds of retinal ganglion cells, the yellow thalamocortical cells reflect sites of crossover between different channels of visual information.