High-quality single crystals of trilayer nickelate La4Ni3O10 were grown at Sun Yat-Sen University in a HKZ furnace at 20 bar oxygen pressure. The samples were used to determine the atomic structure and perform transport measurements under a pressure of up to 44.3 GPa, as the atomic and electronic structure is fundamental to the understanding superconductivity. A tetragonal structural transition is detected at the same time as the drop in resistance below 7 K occurs. DFT calculations revealed that the structural transition results in a significant change of the Fermi surface, showing an intrinsic connection between the structural symmetry, the electronic band structure and HTc superconductivity. Together with the recent discovery of superconductivity under pressure in La4Ni3O10 from Fudan University, this publication reveals further unique properties of this compound, helping to understand the underlying mechanism of superconductivity in nickelates and high-temperature superconductivity in general.