The birth of a manifestation takes place the instant an idea is developed. The moment you have an original idea, you are now creating a brand new experience for yourself that differs from the experience you were creating prior to the formation of the idea.
While you may consider the first physical evidence that your dreams are coming true to be the birth of manifestations, manifestations actually begin to mature at a much earlier stage. As you think an original thought, a thought you have not thought before, you are activating a specific vibrational frequency within yourself, but at this point, the vibrational frequency is singular in nature and not very strong or definite. This is the birthplace of all manifestations though, because after this point, if the manifestation is desirable and you are deliberately directing your thought, you will continue to think this thought and you will continue to think about this thought.
As you think about this thought, you will develop additional yet related thoughts and activate the vibrational frequency of the original thought within yourself more frequently and in a more apparent manner. Then, over time as you continue to expound upon this single thought and make it multiply, the vibrational frequency of the thought will play a large enough role in defining your point of attraction, the way you feel, that a manifestation that matches it, a manifestation that makes you feel the same way these initial thoughts make you feel, will arise.