alchemy of 7

7 planets (Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn)

7 The seven Dhatus (plasma, blood, muscle, fat, bone marrow and reproductive fluid)

in Ayurveda, they are called Sapta Dhatus - Rasa, Rakta, Mamsa, Meda, Asthi, Majja and Sukhra respectively

7 Chakras

7 Colours of visible light spectrum

7 Endocrine Glands

7 Primary Organs (brain, lungs, liver, spleen, kidneys, gold bladder, heart)