Washington ? Scientists can start using taxpayer dollars to do research with 13 batches of embryonic stem cells and the government says dozens more cell lines should be available soon, opening a new era for the potentially life-saving field.

President Barack Obama lifted eight years of restrictions on these master cells last spring. But $21 million-and-counting in new projects were on hold until the National Institutes of Health determined which of hundreds of existing stem cell lines were ethically appropriate to use.

“This is the first down payment,” Dr. Francis Collins, NIH’s director, said Wednesday as he opened a master registry. “People are champing at the bit for the opportunity to get started.”

Thirteen stem cell lines — created by Children’s Hospital Boston and Rockefeller University — are first on that list. Another 96 embryonic stem cell lines are undergoing NIH review, and 20 or more could get a decision by Friday, Collins said.