In this chapter I defend the view that to know what it is like to experience a phenomenal property is just to be consciously acquainted with it, to experience it. Knowledge of what it is like is not knowledge that. It is not conceptual/propositional at all. It does not require thought, or the deployment of concepts. Nor is it knowledge what in the sense of, for example, knowing what time it is, or knowing what the positive square root of 169 is, which is also conceptual. And it is not some kind of know-how. It is, I will argue, simple acquaintance with, being familiar with, a phenomenal property. To know what a particular kind of experience is like is to be familiar with the phenomenal property or properties that characterize it; and to be familiar with such properties is just to experience them. Acquaintance is the fundamental mode of knowledge of phenomenal properties instantiated in experience, it is knowing what it is like; and all it requires is the experience itself.