US scientists have successfully grown fully functioning bladders in the lab, and implanted them into patients with bladder disease.
Other tissues are being cultured
They hope the breakthrough could signal a new era in which a wide range of organs can be grown in the lab.
Who took part in the study?
Seven people with a serious bladder condition caused by a birth defect.
In each case, the patients' bladders were not as pliable as they should have been, and the resulting high pressures risked causing serious damage to their kidneys.
In addition, each had a serious incontinence problem.
Under normal circumstances, the patients would have been considered for reconstructive surgery, in which segments of tissue from the intestines are used to build up the bladder.
However, this carries a high risk of side effects, such as kidney stone formation and cancer.
What did the researchers do?
They took a sample of bladder tissue from each patient, and cultured the cells in a nutrient bath in the laboratory.
The cells were seeded on to a biodegradable bladder-shaped "scaffold" made out of collagen.
Elastic, smooth muscle cells were grown on the outside, with epithelial cells forming the bladder lining on the inside.
After two months the new bladders were fully grown. Each was stitched to the patient's existing bladder to create an enlarged, and more effective organ.
Were the transplants successful?
Yes. The new organs preformed as well as those that have been repaired using more conventional reconstructive surgery.
They appeared free of side effects, and, because the organs were made from the patients' own tissue, there was no risk of rejection.
Why not just opt for a donated organ?
There is a severe shortage of organs for transplant surgery throughout the Western world.
Many people die each year waiting for a donor organ to become available, despite repeated campaigns to encourage more people to donate organs.
It is thought that improved road safety and fewer accidents has contributed to a reduction in available organs.
In the UK, it is estimated that about 6,700 people are on the waiting list for an organ transplant.
However, last year just 2,180 transplant operations took place.
Doctors are also frustrated that attempts to tackle the problem of organ rejection have so far produced fairly limited results.
Will it be possible to grow other types of organ?
In theory. The Wake Forest University team which has pioneered the bladder technique is currently working on ways to grow 20 different tissues and organs.
Scientists have already grown human skin, cartilage, bone and liver outside the body.
However, it may prove to be extremely difficult successfully to culture other fully-functioning organs in the lab.
The bladder is a relatively inert structure, but other organs, such as the heart, are vastly more complex.
In addition, cells from bladders are relatively easy to grow in the lab, whereas no-one has yet been able to make heart cells grow in a similar way.
Professor Peter Weissberg, medical director of the British Heart Foundation, said: "We are still many years away from being able to grow a new heart - if possible at all."
A more likely target might be to grow blood vessels in the lab - like the bladder, they too are relatively inert, simple structures.
Dr Richard Horton, editor of The Lancet, the journal which published details of the new research, said the science of growing organs was still at an early stage.
But he added: "This is a milestone. We just need to be a little cautious, I hope people don't phone up their doctor and say 'how do I get a transplant done next week?'.
"A lot more work needs to go into this, but over the next ten years or so we are going to see a revolution in transplantation."