Maria Anderson | Jun 20, 2004 | 6 min read
HALF A MIND:©2002, The National Academy of SciencesLesioned brains 16 weeks after embryonic stem cell transplant stain positive for tyrosine hydroxylase (TH: green), dopamine transporter (DAT: red), and aromatic amino acid decar-boxylase (AADC: blue) in an overlaid image. Bar equals 25 μm.Since drawing the attention of scientists, ethicists, and policymakers, stem cells have not lost their place as one of the most promising yet controversial scientific discoveries of the 20th century.