"One of the frontier cosmological research themes of the past decade has been the Epoch of Reionization (EoR). This era marked the start of the formation of visible baryonic structures: stars, (dwarf-)galaxies, clusters and the cosmic web. Some top level questions surrounding COsmic REionization are: ""When did it start ?”, “How long did it take ?”, “What were the main ionizing sources ?”, and “What did the Universe look like during this crucial evolutionary phase ?"" Simulations of reionization suggest how it may have proceeded, but hard observational facts on the EoR are few and far between.At the start of the EoR all hydrogen was cold and neutral. At redshift z=6 the transition to an ionized Universe was completed. The 21cm line, redshifted to much longer wavelength, is a key diagnostic during this phase. LOFAR, the European LOw Frequency Array, will be the premier instrument to explore this epoch, simultaneously over the full redshift range from z=6.5-11.5 ! The required angular resolution is also well matched to the 2.5 km CORE of LOFAR. Detecting redshifted HI from the EoR is generally acknowledged as the most difficult radio astronomical project ever attempted. As PI of the LOFAR EoR Key Science Project and as LOFAR Calibration Project scientist, I have worked hard for 10 years to prepare LOFAR and myself for this endeavour.In November 2012 LOFAR commenced a long (> 3-5 years) observing campaign, generating several PB of data per year. A new phase, with extraordinary challenges, still lies ahead. ERC funding for the LOFARCORE team will permit me to ramp up the execution of this program, and in a timely manner (we have competition from US, Australian and Indian groups), solve problems along the way, and analyze and publish what will be ground-breaking results on the COsmic REionization history. The LOFAR EoR project will be the pathfinder for even more daunting future explorations, using SKA, of the phases preceeding the EoR, i.e. Cosmic Dawn."