If a group of things are homogeneous, they're all the same or similar, like a room full of identically dressed Elvis impersonators.
The adjective homogeneous comes from the Greek homogenes, meaning “of the same kind.” You can break down the root of the word further into two parts: homos, meaning “same,” and genos, meaning “kind, gender, race, stock.” It sounds very scientific, but if you look around the table at home and everyone is eating a bowl of oatmeal, you could safely describe your family’s breakfast tastes as homogeneous.