The matter-radiation decoupling ushered the Universe into a period of darkness when its temperature dropped below 3000 K and steadily decreased with the Universe's expansion. The Universe's Dark Ages, as this period is known, ended about 400 million years later, when the first radiation emitting objects (stars, black-holes, etc.) were formed and assembled into protogalaxies during the Cosmic Dawn. The epoch in which the Universe transformed from neutral to ionized is know as the Epoch of Reionization (EoR). The EoR was one the main phase transitions in the Universe.
It is widely acknowledged that the best probe of this important epoch is the redshifted HI 21cm emission line coming from the diffuse neutral hydrogen in the high redshift Universe (z > 6.5). In this talk Professor Zaroubi will review the current understanding of this epoch and the large effort made in order to constrain it observationally. In particular, he will focus on the 21 cm probe and its basic physics. He will then summarize the current observational effort to observe the 21cm radiation from the EoR and the challenges that face it. He will especially focus on the LOFAR EoR project and discuss its potential in uncovering this important event in the history of the Universe.