A recent series of papers have constructed a biochemical pathway that allows yeast to produce opiates. It is not quite a sugar-to-heroin home brew yet, but putting together the pieces looks fairly doable in the very near term. I think I called the news almost exactly five years ago on this blog.
People, including the involved researchers, are concerned and think regulation is needed. It is an interesting case of dual-use biotechnology. While making opiates may be somewhat less frightening than making pathogens, it is still a problematic use of biotechnology: millions of people are addicted, and making it easier for them to get access would worsen the problem. Or would it?