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Using a mesh of points is one of the most intuitive and widely used method for numerically representing spacially resolved quantities, for this reason grids are an efficient and well-established method for solving partial differential equations in many areas of science and engineering.   When simulating electrons using some level of approximation to quantum mechanics, like Hartree-Fock or density functional theory (DFT)~\cite{Hohenberg_1964,Kohn_1965}, different fields needs to be represented numerically: the ionic potential, the single-particle orbitals or states,  and the electronic density. The most popular representations methods are based on the use of basis sets that have a certain physical connection to the system being simulated. In chemistry the method of choice is to use atomic orbitals as a basis to describe the orbitals of a molecule. When these atomic orbitals are expanded in Gaussian functions, it leads to a very efficient method as many integrals can be calculated from analytical formulae~\cite{szabo1996modern}. In condensed matter physics, on the other hand, the traditional basis is a set of plane waves, the eigenvectors eigenstates  of theHamiltonian of a  homogeneous electron gas. These physics-inspired basis sets have, however, some limitations. For example, it is not trivial to simulate crystalline systems using atomic orbitals~\cite{Dovesi_2014}, and, on the other hand, in plane wave approaches finite systems must be approximated as periodic system using a super cell approach. Discretizing in a real-space grids does not benefit from this physical connection to the system being simulated. However they the method has another advantages. In first place, grids  are flexible enough to simulate different kinds of systems. systems, both finite and periodic systems can be directly simulated (including systems with partial periodicity).  A real-space grid has been the traditional way One  ofsolving  the electronic problem on a grid for atomic systems. In this case, radial grids with a non-uniform distribution main advantages  of points working in real-space is that not pose any requirements to the fields that  are used. The idea of modelling polyatomic molecules was pioneered by Becke~\cite{Becke_1989}, who used a combination of radial-grids centered around each atom. to be discretized.  In 1994 Chelikowsky, Troullierm and Saad~\cite{Chelikowsky_1994} presented a practical approach for the solution of the Kohn-Sham equations using uniform grids combined with pseudo-potentials. What made the approach competitive was the use of high-order finite differences, that keep control the error of the Laplacian without requiring very dense meshes.  One A real-space grid has been the traditional way  of solving  the main advantages electronic problem on a grid for atomic systems. In this case, radial grids with a non-uniform distribution  of working in real-space is that not pose any requirements to points are used. The idea of modelling polyatomic molecules was pioneered by Becke~\cite{Becke_1989}, who used a combination of radial-grids centered around each atom.  In 1994 Chelikowsky, Troullier and Saad~\cite{Chelikowsky_1994} presented a practical approach for the solution of the Kohn-Sham equations using uniform grids combined with pseudo-potentials. What made  the fields approach competitive was the use of high-order finite differences,  that are to be discretized. keep control the error of the Laplacian without requiring very dense meshes.  A real-space discretization can be directly applied to the continuum description of the electronic problem. This gives a direct intuition.