This is the worlds easiest and most satisfying thing to grow, and you can grow it anywhere you can fit a window box. All you need is a little sun, and some spinach seeds, and you can have fresh greens in the early spring and through the late fall. They like a coolish ground temperature for germination, like around 60-65 degrees, so depending on where you live you may only be able to grow them in the transitional seasons. Or if you are in the mid-atlantic you can probably grow greens right through the winter.
The trick is that you thickly plant a pot or window box with seeds, don't bother with rows or anything, and then as the leaves get big enough to eat you snip them with scissors leaving the root system intact. Then the smaller leaves below grow to take their place. And if you keep snipping and watering they keep on growing. And the greens really do taste a whole lot better when they are home grown than the ones in the box from the store. It works with other types of baby green too. So if you have room for a window box you can have a tiny garden with really very little effort. And they grow so close together you don't even ever have to weed them. It is truly no fuss.