Novel adult liver progenitor cells (called H2Stem Cells) have been have been characterized on the basis of a series of biological activities and markers. Methods for producing H2Stem Cells allow providing such cells in the form of adherent cells and three-dimensional cell clusters in suspension that can be differentiated into cells having strong liver-specific activities and/or that can be used for treating liver diseases or for evaluating the efficacy, the metabolism, and/or toxicity of a compound.