We report on the recent development of pioneering, unified, all-particle calculations of the ground state energiesGround state energy of a quantum mechanical, three-body atomic system, an exotic system and a molecular system using two different numerical tensor methodsNumerical Tensor Methods (NTM) (NTM), namely the Lagrange-mesh NTM [20], and the LaguerreLaguerre series solution method (series solution) NTM [21], both utilizing explicitly correlated wave functionsExplicitly correlated wave functions. It is shown that energies of at least nano-Hartree accuracy can be obtained with very low computational cost. The methods are put into context by reviewing the emergence of Quantum Chemistry DMRGDensity Matrix Renormalization Group (DMRG) and NTMsNumerical Tensor Methods (NTM) in the past two decades and emphasizing how the two methods are related to well-known variational methods, series solution methods and finite-element methods.