All things in our physical world were first created spiritually:
...For I, the Lord God, created all things, of which I have spoken, spiritually, before they were naturally upon the face of the earth.... (Moses 3:5)
For example, we read how God created all plants before they existed here:
4 These are the generations of the heavens and of the earth when they were created, in the day that the Lord God made the earth and the heavens,
5 And every plant of the field before it was in the earth, and every herb of the field before it grew: for the Lord God had not caused it to rain upon the earth, and there was not a man to till the ground. (Genesis 2)
As another example, the Lord told Jeremiah that he existed as a spirit before he was born:
Before I formed thee in the belly I knew thee; and before thou camest forth out of the womb I sanctified thee, and I ordained thee a prophet unto the nations. (Jeremiah 1:5)
Not everything that exists or can exist spiritually has been manifested in the physical world:
31 For by the power of my Spirit created I them; yea, all things both spiritual and temporal—
32 First spiritual, secondly temporal, which is the beginning of my work; and again, first temporal, and secondly spiritual, which is the last of my work—
33 Speaking unto you that you may naturally understand; but unto myself my works have no end, neither beginning; but it is given unto you that ye may understand, because ye have asked it of me and are agreed.
34 Wherefore, verily I say unto you that all things unto me are spiritual, and not at any time have I given unto you a law which was temporal; neither any man, nor the children of men; neither Adam, your father, whom I created. (D&C 29)
Faith is the mechanism that creates in the spirit and that, from spirit, creates in the physical world.