Inside a Solar Yard Light

You can see the battery, LED and controller board. If you cover the light sensor, the LED turns on, like this:
Here are close-ups of the LED and the controller board:

On the other side of this module is a four-cell solar array, measuring 2 inches by 2 inches (5 cm x 5 cm), and the photoresistor:

Here is a closer view of the photoresistor:

See How do the streetlights turn on automatically at night? for more information on how photoresistors work.
Now let's see how the whole setup works to light your yard at night.