Yod is the tenth letter of the Hebrew Alphabet, a tiny marking much like ( ' ), and is very interesting.
The Mystery of Yod -
Suspended in mid-air, Yod is the smallest of the Hebrew letters, the “atom” of the consonants, and the form from which all other letters begin and end. [The first dot with which the Scribes first start writing a letter, or the last dot that gives a letter its final form – is a yod. (Likutei Maharan).] In the Jewish mystical tradition Yod represents a mere dot, a divine point of energy. Since Yod is used to form all the other letters, and since God uses the letters as the building blocks of creation, Yod indicates God’s omnipresence…Since Jesus upholds the world by the Word of His power (Hebrews 1:3), and Yod is part of every Hebrew letter (and therefore every word), Yod is considered the starting point of the presence of God in all things – the “spark” of the Spirit in everything.
from the Kabbalah Unveiled
7. When the inferior man descendeth (into this world), like unto the supernal form (in himself), there are found two spirits. (So that) man is formed from two sides--from the right and from the left.
8. With respect unto the right side he had NShMThA QDIShA, Neschamotha Qadisha, the holy intelligences; with
respect unto the left side, NPSh ChIH, Nephesh Chiah, the animal soul.
[These answer to the right and left pillars of the Sephiroth. See Introduction.]
9. Man sinned and was expanded on the left side; and then they who are formless were expanded also. (That is those spirits of matter, who received dominion in the inferior paths of the soul of Adam, whence arose base concupiscence.) When (therefore) both were at once joined together (namely by base concupiscence, together with connexion, and the animal soul) generations took place, like as from some animal which generateth many lives in one connexion.
10. (There are given) twenty-two letters hidden and twenty-two letters manifested (which are the symbols of those sublime forms).
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11. (The one) Yod is concealed; the other is manifested. (The one is the understanding or mother, the other is the kingdom or queen; so that at the same time it looketh back to the superior paths.) But that which is hidden and that which is manifest are balanced in the equilibrium of forms. (That is, masculine and feminine; the one, the father and the mother; the other, the foundation and the queen; meaning principally the female idea, which includeth form and receptacle.)
12. Out of Yod are produced male and female (if, namely, it be fully written as IVD, Yod, they are then its augment), Vau and Daleth. In this position Vau is male, and Daleth is female. And hence arise DV, the two letters which are the duad male and female; and not only the duad, but also the co-equal duads (of the superior and inferior conjunctions).
13. Yod by itself is male (the father); He, female (the mother).
Yod as the primal vibration of the universe out of which all the other letters came forth. Thus Yod also contains the seed of the Tree of Life, of all the Sephiroth and the Paths. It symbol is the hand. When the hand is open it represents the microcosm, and man in the lower worlds; when the hand is closed, it represents unity, the source. Yod is the tenth letter, and two hands have ten fingers. It numerical value is 10 + 6 + 4 = 20, which is two times ten, or just two, pointing to duality.