The retina has become the latest human body part to be grown in the lab.

German researchers have shared a new recipe for making human retinas - the part of the eye that is sensitive to light.

They demonstrated the technique by generating retinal cells in laboratory plates, as well as complex tissue in the form of tiny eye-like cups.

The tiny 3-D retina organoids mimic the organ's natural tissue organisation and have been produced, from mouse and human stem cells.

Once-controversial stem cell technologies can be used for the treatment of all sorts of diseases, and as clinical researchers work to apply the cells into new therapies, stem cell biologists on the cutting edge are even working to understand the regeneration of neurons and other highly-complex cells.

For example, the retinal organoids developed at the German Centre for Neurodegenerative Diseases (DZNE), specifically include the light-detecting cone cells, which now can be produced in high quantities in their mini-retinas.

Cone photoreceptors, which are responsible for high acuity and colour vision, are the most precious retinal cell type with regard to potential future cell replacement therapies in patients affected by retinal degeneration.

The new mini-retina production technique involves cutting a retina organoid grown from stem cells into three pieces at an early stage of eye development.

Each of these pieces, which look like little half moons, eventually grows into the full suite of cells found in the retina, increasing the yield of retinal organoids up to 4-fold.

A trisection also spurs the surviving organoids to grow to reach sizes similar to uncut organoids. These mini-retinas swim around in the dish and because they are not attached to a surface, and so they better reflect the structure of retinal tissue during development.

The next objective is to make the ‘mini-retinas’ even more complex, perhaps by bringing in blood vessels, as well as to use the organoids to study regeneration and the function of different neural cell types - specifically, from the human retina.

The full study is accessible here.