The present invention relates to an in vitro method of producing a bi- or multi-differentiated tissue with at least two tissue types comprising the steps of developing a first tissue to a stage of differentiation of interest, developing a second tissue to a stage of differentiation of interest differing from the stage of differentiation of interest of the first tissue, placing said first and second tissue in a vicinity sufficient for fusion by growth, allowing the first and second tissue to grow and fuse to each other, thereby producing a bi- or multi-differentiated tissue comprising the first and second tissue with different stages of differentiation ; bi- or multi-differentiated tissue obtained by such a method; uses of the tissue and kits for performing the method.