Gravitational lensing is predicted by Albert Einstein's general theory of relativity almost a century ago. It took 40 years till it was observed for the first time in 1979. It can be explained with older methods like apple and candle If you put an apple between you and the candle flame you will not see the flame. Moving your point of view up a bit, you can see behind the apple. However, if that apple is very massive it will bend the light and you will see that very same light without moving. So, in other words put something heavy enough in front and you will be able to see some things behind it. Even better, there is some magnification!

How heavy this apple should be?  Blackhole scale at least, but it is much easier with heavy galaxies clusters. They are like telescopes in space and we are looking through them Well, in fact there are more requirements in order the scope to be in focus - the lens mass, the distance between us and between the lens and the object are connected. So, not every galaxy cluster could provide a good view for us, most of the time there is nothing in the lens sweet spot or we are looking in the lens from too close or too far

This is not the case with Cheshire Cat - we have well focused imagen produced by the gravitationl lens of a galaxy cluster! The "eyes" and the "nose" are huge elliptical galaxies dominating the small cluster SDSS J103842.59+484917.7 which is around 4.6 billion light years from us. Their light recorded in this image was emitted around the time our Sun was forming! The "smile" and the left contour of the face are the lens magnified images of four distant galaxies behind the eyes! Measuring the red-shift (0.966 according to https://iopscience.iop.org/article/10.1088/0004-637X/761/1/1/pdf) of these "images" is considered that background galaxies are around 10.1 billion light years away !!!

So, by double stacking my 250mm telescope with the SDSS J103842.59+484917.7 "space telescope" is possible to see something 10 giga light years away! What a travel in space and time!!!

P.S. The reference image in bottom right is taken with a real space telescope - Hubble...

https://www.astrophotography.app/