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Video abstract for the article 'Formation of heavy d-electron quasiparticles in Sr3Ru2O7' by M P Allan, A Tamai, E Rozbicki, M H Fischer, J Voss, P D C King, W Meevasana, S Thirupathaiah, E Rienks, J Fink, D A Tennant, R S Perry, J F Mercure, M A Wang, Jinho Lee, C J Fennie, E-A Kim, M J Lawler, K M Shen, A P Mackenzie, Z-X Shen and F Baumberger M P Allan et al 2013 New J. Phys. 15 063029 Read the full article in New Journal http://iopscience.iop.org/1367-2630/15/6/063029 . GENERAL SCIENTIFIC SUMMARY Introduction and background. The unusual physics of the bilayer ruthenate Sr3Ru2O7 exemplifies some of the unsolved problems in condensed matter physics. Its rich phase diagram includes quantum criticality, magnetism and an electron nematic phase. It has been speculated that many of these phenomena are related to a strong mass renormalization of the Ru 4d electron liquid. However, microscopic insight into the formation of heavy quasiparticles from the extended 4d electrons was largely missing. Main results. We use angle-resolved photoelectron spectroscopy measurements to provide microscopic insight into the formation of the strongly renormalized heavy d-electron liquid that controls the physics of Sr3Ru2O7. Our data reveal itinerant Ru 4d-states confined over large parts of the Brillouin zone to an energy range of less than 6 meV, nearly three orders of magnitude lower than the bare band width. We show that this energy scale agrees quantitatively with a characteristic thermodynamic energy scale associated with quantum criticality and illustrate how it arises from a combination of back-folding due to a structural distortion and the hybridization of light and strongly renormalized, heavy quasiparticle bands. The resulting heavy Fermi liquid has a marked k-dependence of the renormalization which we relate to orbital mixing along individual Fermi surface sheets. Wider implications. We show that in a multi-band system, such as Sr3Ru2O7, local electron correlations can cause a strong mass enhancement with a pronounced anisotropy in k-space. We expect that this effect is of general relevance to 4d transition metal oxides and other strongly correlated multi band systems. The microscopic origin of this behavior in Sr3Ru2O7 is reminiscent of Kondo-type heavy fermion materials, and might allow the discovery of common ground between these very different families of materials.