He announced Friday that he will allow greater federal funding for stem cell research, following through on a campaign promise he made in 2008.
President Bush restricted federal money for research in early 2001.
Work with stem cells is considered controversial because embryos are destroyed to obtain the cells. But scientists say allowing greater stem cell research could teach them how to treat or even cure various conditions and unravel more of the mysteries of human development.
The president is expected to sign an executive order at the White House on Monday.