The whole purpose of yoga is to transform and divinise human life and hence the working is on a vast field and area of life. In this sense it is a laboratory of spiritual evolution.
The Overmind is the line where the finite world parts from the infinite, the temporal time bound hemisphere of existence parts from the eternal hemisphere that alone can make our life whole.
They met on the 29th March 1914 when time and circumstance conspired to open the doors of destiny. The veil was rent almost instantaneously and the recognition followed. A new matrix of time had begun.