Many scientists believe stem cells hold great promise for new treatments
US regulators have approved 13 new lines of human embryonic stem cells for use in scientific research.
They are the first batches of embryonic stem cells - the building blocks of the body - that have been made available to US researchers in almost a decade.
The move comes after President Barack Obama eased restrictions on federally funded embryonic stem cell research.
Another 96 lines could soon be approved if they meet the ethical guidelines unveiled in July, US scientists said.
Scientists hope to harness the cells to treat a variety of diseases, including injuries, cancer and diabetes.
"I am happy to say that we now have human embryonic stem cell lines eligible for use by our research community under our new stem cell policy," said Francis Collins, director of the US National Institutes of Health.
Embryonic stem cells come from days-old embryos and can morph into any type of cell in the body.
Each embryo yields one stem cell line - a family of cells which can be replicated indefinitely in a laboratory.
But their use in scientific research is controversial. Opponents say culling the cells is unethical, as it destroys the human embryo.
Under former President George W Bush, federal funding was limited to about 60 stem cell lines created from embryos destroyed prior to August 2001.
Scientists say the new lines were created in ways that made them far better candidates for successful research.
The US government unveiled ethical guidelines for the research in July, requiring full parental consent and limiting scientists to using existing embryos that would otherwise be destroyed.
In keeping with the guidelines, the 13 newly-approved lines were created using private money from leftover embryos at fertility clinics.