Skin grown in the laboratory can replace animals in drug and cosmetics testing, UK scientists say.
Skin has a natural barrier that keeps water in and microbes out
A team led by King's College London has grown a layer of human skin from stem cells - the master cells of the body.
Stem cells have been turned into skin before, but the researchers say this is more like real skin as it has a permeable barrier.
It offers a cost-effective alternative to testing drugs and cosmetics on animals, they say.
The outermost layer of human skin, known as the epidermis, provides a protective barrier that stops moisture escaping and microbes entering.
Scientists have been able to grow epidermis from human skin cells removed by biopsy for several years, but the latest research goes a step further.
The research used reprogrammed skin cells - which offer a way to produce an unlimited supply of the main type of skin cell found in the epidermis.
They also grew the skin cells in a low humidity environment, which gave them a barrier similar to that of true skin.
Lead researcher Dr Dusko Ilic, of King's College London, told BBC News: "This is a new and suitable model that can be used for testing new drugs and cosmetics and can replace animal models.
"It is cheap, it is easy to scale up and it is reproducible."
He said the same method could be used to test new treatments for skin diseases.
New skin cells were grown by turning back the clock of adult cells
Researcher Dr Theodora Mauro said it would help the study of skin conditions such as ichthyosis - dry, flaky skin - or eczema.
"We can use this model to study how the skin barrier develops normally, how the barrier is impaired in different diseases and how we can stimulate its repair and recovery," she said.
The Humane Society International, which works to protect animals, including those in laboratories, welcomed the research, published in the journal Stem Cell Reports.
Research and toxicology director Troy Seidle said: "This new human skin model is superior scientifically to killing rabbits, pigs, rats or other animals for their skin and hoping that research findings will be applicable to people - which they often aren't, due to species differences in skin permeability, immunology, and other factors."