Hydrogen intensity mapping of the 21cm line holds the promise of mapping the
large scale structure of the universe at the largest scales and the furthest redshifts, even well before galaxies have formed. While no convincing demonstration of this technique has yet been made there are several experiments in progress which are hoping to demonstrate this technique. I will discuss the progress made so far and plans for the future of Tianlai Project which operates a highly configureable purpose built interferometer in western China.
SOM