The seventh and final chakra of the physical body is the Crown Chakra. The Sanskrit is Sahasrara, the thousand petaled lotus. 
The color is ultraviolet. In the 7 colors of the rainbow, beginning red at the Root Chakra upwards towards the indigo of the Third Eye, ultraviolet is just beyond the visible spectrum of light. Oftentimes people receiving a Reiki session or meditating with the energy will see in their minds eye iridescent light purple. I believe that this indicates the opening of the crown chakra, becoming aware of the connections tha we have with one another. This is common when one is in the frequency of Reiki.
Body parts are top of head, pituitary gland, the brain, and the skin. 
The pituitary gland is “the master gland” in the endocrine system. it regulates all the other glands, including the thyroid (throat chakra), adrenals (root chakra),  pancreas (solar plexus chakra), among others. 
The skin is our last barrier between our individual selves and the outer world. 
Energetic location is just above the top of the head. Nature is already in harmony with the Universal Life Force energy and when you spend time in nature settings, it amplifies your connection to Reiki. I visited the Lincoln Park Conservatory in Chicago the day after my first Reiki attunement in 2010. As I stepped into the building full of lush and teeming plant life, I immediately felt my crown chakra open and expand.

The element is the most intangible of all the elements: thought. 
Universal consciousness, All-is-One, Higher Power, connection to what lies beyond the physical to all of humanity and the source of all life. The thousand petaled lotus that touches on all possibilities and potentialities. Similar to the root chakra, it is a gateway, but to our potential and what is yet to come. 

Crown Chakra Image by Peter Lomas from Pixabay