An estimated 500,000 hobbyists in North America are making wine with purchased grapes, juice, even berries. Some even grow their own. By Eric Asimov Reporting from Geyserville, Calif., and New York.

Have you ever glanced at the grapes on a cheese plate and glass of wine in your hand, and wondered how grapes turn into the delicious elixir you are gently sipping? Yes, you may know wine is ...