Add this to the list of things you can grow in a petri dish: An honest-to-goodness mini-kidney.

Australian scientists have successfully developed a method that allows mini-kidneys to be grown from stem cells in a lab — an achievement that could help with drug research, as well as one day possibly providing assistance to those in desperate need of a kidney transplant.

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Minoru Takasato (left) and Melissa Little. Image: University of Queensland

Using stem cells derived from human skin cells known as fibroblasts, the team "encouraged" the cells to form a miniature organ, Melissa Little, a professor at the University of Queensland, told Mashable Australia. The research was published in Nature.

"It's a bit like cooking, but we spend a lot of time getting the ingredients right," she added. Typically, the mini-kidneys take 18 days to develop.

Once grown, the mini-kidneys are visible without a microscope at between half-a-centimetre and one centimetre in width. A human kidney, on the other hand, is about the size of grapefruit, Little said.

An adult kidney also has around 1 million nephrons — the structures that perform the important filtering function of the kidney — while the researchers' creation contains around 50 to 100 nephrons. The lab-generated organs are also missing the waste drainage outlet that's vital to kidney function in an adult.

Rather, the mini-kidneys are similar to those found in a foetus around the early second trimester. "We estimate that they're equivalent to a 10 to 13 week foetus," Little said. "It's got all the cell types present at that stage of development."

Kidney organoid in a dish generated from human pluripotent stem cells. The three colours show the presence of distinct cell types within the developing nephrons. Image: Fabian Fromling and Minoru Takasato

While there's a long road ahead for the scientists if they are to grow an adult-sized kidney, Little said their findings could be useful right away.

A mini-kidney could be grown from the cells of someone with kidney disease, for example, so doctors could run tests and better understand the individual's illness. Alternatively, drugs could be tested on the lab-created organ to find which medications would be most effective for the patient.

Will it one day make a viable organ transplant? Certainly, Australia could use the help. According to Kidney Health Australia, one in three Australians is at an increased risk of developing chronic kidney disease, and the average wait time for a transplant is around three-and-a-half years, but can be up to seven years.

"I'd love to see that happen in my lifetime," Little said. She suggested it might also be possible to take some of the stem cells, and put them into a patient whose kidney is malfunctioning to help fix it.

There are still many unknowns about that process, however. "We don't know whether they'll go in the kidney and do the right job, but what we know is we have an ability to make cells that might be useful," she said.