The Moon appears to Earth as a small crescent, as it rotates around the Earth this expands to a full moon and back to a small crescent. This happens once every 29 days and is called a lunar month. The Moon causes the rise and fall of the ocean's tides on Earth.
"Grandmother cells" are mostly closely associated with specificity coding. Specifity coding is the representation of particular objects in a particular environment by the firing of neuron that are tuned to respond specifically to that object. Single cells fires only in response to the presence of a particular face say a grand mother but no response to any other face.