The next big issue for the federal health law as it moves toward implementation is how regulators will define so-called essential benefits—the basic medical services that health plans must cover under the law. The legislation gives 10 categories of care that plans must provide for customers of the health-insurance exchanges that are launching in 2014. But the law leaves details up to regulators, who are now starting to develop the rules. Habilitative services have become a contentious point in the debate. Unlike rehabilitation, which helps patients recover skills they have lost, habilitation helps patients acquire new skills. Such services can be costly because the process can take years, and insurers haven't typically covered many of them, sometimes labeling them educational or experimental. The debate over exactly what habilitative services to include in the new rules—and how much of them—exemplifies the challenge of defining what health benefits are truly essential.