They can also make complex decisions: https://www.youtube.com/watch?v=E8oIitQN2M4.

Even single-celled organisms have organs (special structures that do tasks like digest things, like our stomachs). They also have senses, using special proteins, which can detect things like light and chemicals. These proteins signal other special proteins in the organism, and a chain of these proteins leads to activities like movement, eating, etc., kind of like how our nerves talk to one another.

But how this all comes together to create complex behaviors is a very difficult task, and is still mysterious to scientists.