From the Technology Review: "In a bid to harness the potential of embryonic stem cells, surgeons in California have implanted lab-grown retinal cells into the eyes of two patients going blind from macular degeneration. ... The two patients, whose names weren't released, are among the first volunteers ever to receive a treatment created using embryonic stem cells. ... We are excited about this treatment, because we think this has the potential to slow the disease progression. This company has had their ups and downs, and I am really happy to see they got into the clinic. We've had our fingers crossed. ... During a recent visit to Advanced Cell's laboratories, a research technician adjusted a microscope to show off the company's lead product: cube-shaped retinal pigment epithelial cells growing in a petri dish. Some were translucent, while others already had the brownish coloring of a mature cell. (The pigment absorbs stray light in the eye, acting as a kind of glare shield.) These retinal cells are the type that are killed off in macular degeneration, eventually leading to the death of photoreceptors, and the gradual loss of central vision. Advanced Cell believes that injecting new, lab-grown cells into the eye may cure the condition. ... It's no accident [that] both early studies of embryonic stem-cell therapies - those of Geron and Advanced Cell - involved cells of the nervous system. The reason is that embryonic stem cells naturally want to make neuroectoderm, a cell lineage in the embryo that forms the nervous system. ... Embryonic stem cells have a mind of their own, and they want to do certain things ... Efforts to produce other cell types, such as liver cells, have proved far more difficult."