There is something it is like to have a phenomenal experience, e.g., see and taste and hear water rushing down a stream; such experience is subjective, immediately knowable, and unified. In these ways it is unique and seems utterly different from the objective phenomena that are the usual subject of scientific investigation. My research plan is to investigate the nature and origin of the concepts that we apply in introspection to refer to such experiences. These concepts, called "phenomenal concepts", are roughly expressed in words as "this sensation". My interest in phenomenal concepts is motivated by my conviction that understanding their nature holds the key to settling the mind-body problem – the problem of how the mind, and especially, phenomenal experience relates to the rest of nature, and more specifically, to the brain. I think the mind-body problem can be solved if we consider the special cognitive mechanisms involved in introspecting our experience, i.e., if we focus on the nature of phenomenal concepts.