Luminous quasars have been detected well into the epoch of reionization, probing the existence of super-massive black holes (SMBH) less than a Gyr after the Big Bang, and setting strong constraints on the the first crucial phases of the build-up of SMBHs and their host galaxies. To form a SMBH in such a short time scale, the first quasars need to be embedded in abundant cold gas reservoirs able to continuously feed the growth of the first black holes. This key ingredient of the galaxy formation could be mapped at z>6 through the detection of an extended and diffuse LyAlpha emission that appears when the cold gas is fluorescently illuminated by the emission of a bright quasar and/or by the UV-photons generated by an intense star formation event. I will present our efforts to directly observe this feature and thus to probe the environment where supermassive black holes can form in the early Universe.