In most literature, these subtle bodies can be confusing as there are different names and levels away from the physical body. If you can try to see the subtle bodies as an x-ray, your physical body is the bone and hard tissue you usually see on an x-ray. These subtle body layers are you, but from a different focus, ie: you only see the body not the bones inside. Subtle bodies are linked to the mental, physical and spiritual aspects of you.
The more your energy spreads out into the Universe, the more aware you are. If you visualise each energy level like a layer of a glass window, what would happen if it got dusty and dirty? The desired state is to have as little dirt and dust on the glass window as possible. If you only look at this from a human consciousness, it limits your perception of the subtle body system. The aura is a sum total of all non-biological bodies. Some aspects of the aura can be measured, ie: heat. Biomagnetics can also be measured (nervous system) and it has recently been found that cells communicate by light (protons).
The subtle bodies are like echoes and memories of you which have got stuck throughout your lifetime, like dust on the glass window or a scratch on a CD. With crystal therapy, I work with the energies of these subtle bodies which help to 'spring clean' any dust and debris which has settled and may be causing imbalances.
Below is an explanation of the levels of the subtle bodies:
Etheric Body (Base Chakra) 1st Level (Rigid)
This is an exact replica of physical body including organs but in another form. It looks very much like the physical form and will show as electric blue in colour. It also shows up impending problems as it is the last level before imbalances manifest into the physical body.
Emotional Body (Sacral Chakra) 2nd Level (Fluid)
This is you as an emotional being and is much more fluid than the Etheric body and tends to be the layer mediums/clairvoyants will see. This layer shows up on aura photos (Kirlian Photography) like swirls of colour which change as your moods change.
Mental Body (Solar Plexus Chakra) 3rd Level (Rigid)
This is the self through focus of thoughts, beliefs and how we make sense of data and information. This body is more structured and rigid. It relies on patterns and pictures. Shows as yellow or bright yellow but can have areas of dark or show shapes.
Most sources agree on the first three levels. However, there are some anomalies with the following layers:
Astral Body (Heart Chakra) 4th Level (Fluid)
This is like a gateway to the other levels. It is the last level where the sense of you and your personality is familiar. The Astral body is the part of the subtle body system that holds you together in this time and space. It is the barrier that prevents too much past information getting into the lower three levels. It is to do with self, relationships and the ability to maintain boundaries. It is very similar to the Emotional body but there is more of a subtle flow of energies and colours.
Causal Body (Throat Chakra) 5th Level (Rigid)
Finer levels of communication.
Soul Body (Brow Chakra) 6th Level (Fluid)
Thoughts and symbols.
Spiritual Body (Crown Chakra) 7th Level (Rigid)
All of you together.