Two separate teams of scientists have successfully grown mini-brains and mini-kidneys in a Petri dish.

Researchers from Ohio State University announced that they have grown an almost complete embryonic brain, which was equivalent to 98 percent of the brain of a five-week-old fetus. Technically speaking, it was not a brain, but pieces of tissues or organoids grown in a Petri dish, according to CNN.

These lab grown mini-brains are small, as each piece measures two to three millimeters long. The scientists used skin cells to grow them.

"It not only looks like the developing brain, its diverse cell types express nearly all genes like a brain," Rene Anand, professor of biological chemistry and pharmacology at Ohio State University, said in a press release.

The scientists said that these brain organoids could help test medications and treatments against diseases like autism, Alzheimer's diseas and Parkinson's disease. They could also be used in studying conditions like schizophrenia and post-traumatic stress disorder.

Meanwhile, another group of scientists from Australia were also able to grow mini-kidneys in a lab. These organoids were equivalent to human kidneys during the first trimester of development. They were also developed using human skin cells.

The researchers said that the kidney organoids would be useful in testing for the toxicity of new drugs. In developing new medicines, scientists often use animal experiments to test if the compounds used are toxic to the kidney. However, this method is not accurate, as many new drugs fail in clinical trials because of kidney toxicity.

"The great hope is that drug companies will use the new lab-grown kidneys to screen drugs," Jamie Davies, professor at the University of Edinburgh who was not involved in the study, told The Wall Street Journal.

However, lest people get the wrong idea that scientists are creating a Frankenstein, the scientists said that the lab grown mini-brains and mini-kidneys are far from being fully grown brains and kidneys.

The brain needs a vascular system to be complete. For a kidney to be complete, it needs over 20 different cell types, whereas the one grown in the lab only has 12. The kidney's nephrons also need to be connected to a functional draining system in order to be considered as a true kidney.

"They are not capable of growing beyond where they are," Anand said, referring to the mini-brains. "We have no intention of going beyond that."

On the other hand, kidney organoid lead researcher Melissa Little, development biologist at the Murdoch Children's Research Institute in Melbourne, said that the research team wants to develop a bigger kidney. The team is hoping to create a lab grown kidney that can be used in transplants. Patients relying on dialysis only benefit from about 10 percent of kidney function.

"If we can replace even a quarter of kidney function, we'd be doing better than dialysis," Little said.

The Australian researchers published their findings in the Oct. 7 issue of the journal Nature.