When, in the 20th century, cell biologists learned to grow tissue samples in the laboratory, it transformed our understanding of how cells grow and how they react to disease. Crucially, it allowed us to test drug treatments on living cells before risking them in a person.
But tissue samples growing in petri dishes are two dimensional; they are poor substitutes for the solid organs in our bodies. So scientists have recently started coaxing cells to grow in three dimensions. The blobs of tissue they create are called organoids; they are not fully-functioning organs, but nor are they mere sheets of cells. There are organoids of heart, kidney, liver, breast, retina and even brain tissue.
Scientists use organoids to examine organ development and growth and, when investigating diseases such as cancer, the effect of genetic tweaks can be much more easily assessed. The dream, however is to grow organoids in the lab and transplant them into our bodies to replace damaged or diseased tissue. If you have kidney disease, you could get a transplant of a brand new kidney grown from your own tissue. If you have heart disease, you might get healthy new heart tissue. Or if you have a brain injury or degenerative disease such as Parkinson's or Alzheimer's, it might even be possible one day to have your brain augmented with a brain organoid.