The challenges of growing food in the city -- pretty much any city, really -- are well documented, and topping the list of obstacles is the issue of space. In packed metropolises like New York, where back yards, patios, and roof decks are something of a luxury, finding the necessary square footage beneath adequate sunlight can be a tall order. Still, determined growers make due, farming in container gardens on their front stoop, snagging a coveted plot in a community garden, sneaking their crops onto roofs and fire escapes, maintaining small windowsill gardens, and even engaging in some guerrilla gardening in unused public space. Commercially, rooftop farms and indoor farming techniques are becoming increasingly popular means of supplying urban dwellers with fresh, locally grown produce.