A tissue structure for enabling comprehensive understanding of gene patterns of mature cells and a method of preparing the tissue structure are provided. A tissue structure is obtained by co-culturing an endodermal, ectodermal, or mesodermal cell derived from a stem cell and at least one cell and/or factor selected from the group consisting of a vascular cell, a mesenchymal cell, a factor secreted by a vascular cell, a factor secreted by a mesenchymal cell, and a factor secreted when both a vascular cell and a mesenchymal cell exist. A value obtained by assay of a plurality of functions using a Pearson product-moment correlation coefficient is closer to a value of a cell or biological tissue sampled from an adult than a value of a cell or biological tissue sampled from a fetus.