An enlightened friend has taught me of the four 'life elements.' Those are Earth, Water, Fire, and Air/Ether. Each of these elements can be
represented in the physical world, however what's 'physical' is merely a reflection of the spiritual. I'll try to break it down.
Earth represents the body, or form. It's what our five senses can perceive, also known as the physical universe. To go a bit deeper, it's all
vibrations caused by the echo of true formless reality.
Water is emotions. The result of the battle between mind and spirit. Chemical reactions.
Fire is action, or sacrifice. Through fire, organic matter is burned away, creating Ether.
Air/Ether is pure spirit. This is actually a tough one to describe. Air is represented physically by breathing. As breathing can be controlled
consciously (vs heartbeat, digestion, etc) it's considered to be the true link between form and spirit. If Fire is action, Air is meditation.
The human form is composed mostly of Earth and Water. In able to become spiritually enlightened, we must introduce Fire and Air into our lives. Allow
me to quote from the Isha Upanishad
"In dark night live those for whom the world without alone is real; in night darker still, for whom the world within alone is real. The first leads
to a life of action, the second to a life of meditation. But those who combine action with meditation cross the sea of death through action and enter
into immortality through the practice of meditation. So have we heard from the wise."