In the words of David Chalmers, “Consciousness poses the most baffling problem in science. There is nothing that we know more intimately than conscious experience, but there is nothing that is harder to explain. All sorts of phenomena have yielded to scientific investigation in recent years, but consciousness has stubbornly resisted. Many have tried to explain it, but the explanations always seem to fall short of the target. Some have been led to suppose that the problem is intractable, and that no good explanation can be given.”

Let’s start with reviewing the experience of color. Thermonuclear reactions in the sun produce photons – carrier particles of electromagnetic energy. The photons propagate towards earth and eventually hit optic nerve in our eyes. The optic nerve, in response, generates electrical signals that travel further along the neural pathways of the brain. The neural cells get excited and start firing even more electrical impulses. This entire cascade of electrochemical activity is a purely physical phenomena, and, despite being undoubtedly difficult to trace and decode in details in a lab, represents absolutely no fundamental conceptual problem. But suddenly, if as by magic, in the midst of this purely physical phenomena, arises an experience of redness – e.g., the perception, awareness, and experience of a color.

What do we make out of this? The big 3 questions immediately come to mind: 1) where is this experience to be found? 2) what is experiencing this? and 3) why and how purely physical phenomena is accompanied by any subjective experience at all?

1) Where is this experience of redness to be found? It’s thought that it resides somewhere in the volume of space occupied by the brain. But imagine we could magnify the brain to such an extend that we could simply walk into it. What would we see around us when inside? We would see a cellular structure. We would see the cells themselves here and there. We would see some flashes of electromagnetic energy between the synapses of the cells. We would see lots and lots of empty space. We would see some molecules moving in all directions. But would we see redness there? Would we see enjoyment of redness there? Pain? Falling in love with it? Fear of it? No, we would not.

2) What in the brain is experiencing redness? The neural cells of the brain? The chemical and electrical activity? Information processing and integration done by the cells? The empty space between the cells? Molecules that make up the cells? Chemical bonds between the molecules? Quarks and electrons that make up the molecules? Some quantum effects? Name any physical concept you want and ask yourself if it is capable of experiencing redness.

3) Why and how purely physical phenomena is accompanied by any subjective experience at all? Gary Gutting – a philosopher, powerfully demonstrated the predicament: consider Mary, a leading neuroscientist who specializes in color perception. Mary lives at a time in the future when the neuroscience of color is essentially complete, and so she knows all the physical facts about colors and their perception. Mary, however, has been totally color-blind from birth. Fortunately, due to research Mary herself has done, there is an surgical operation that gives her normal vision. When the bandages are removed, Mary looks around the room and sees a bouquet of red roses sent by her husband. At that moment, Mary for the first time experiences the color red and now knows what red looks like. Her experience, it seems clear, has taught her a fact about color that she did not know before. Before this she knew all the physical facts about color and its underlying mechanism, but not the experience of redness. Therefore, there is a fact about color that is not physical and physical science cannot express all the facts about color and other subjective experiences that accompany purely physical phenomena.

No one has a slightest idea how answer these big 3 questions – because simply, they are utterly incomprehensible to everyone who deeply thinks about them. In the several millennia of attempting to find an answer, it’s not even been conceived in a very rough and the most general outline. Literally all attempts from the materialistic perspective to approach these questions have been shown to be completely unsatisfactory.

the above is an except from the article:
https://theproblemofconsciousness.wordpress.com/