An in vitro method of inducing formation of a gastric fundus tissue, wherein the gastric fundus tissue is a fundic type of gastric epithelium found in the corpus that contains fundic cell types, including but not limited to acid-producing parietal cells and protease-producing chief cells, comprising the steps of: a) contacting an adherent mammalian definitive endoderm cell with a wnt signalling pathway activator, an FGF signalling pathway activator, a BMP signalling pathway inhibitor, and retinoic acid, for a first period; wherein the wnt signalling pathway activator is CHIR99021; the FGF signalling pathway activator is FGF4; and the BMP signalling pathway inhibitor is Noggin; wherein said first period is three days ± 24 hours and wherein said retinoic acid is added for the third day of the first period ± 24 hours to form a three-dimensional posterior foregut spheroid in suspension from said adherent definitive endoderm; b) suspending said three-dimensional posterior foregut spheroid in a basement membrane matrix with a growth factor, said wnt signalling pathway activator, an EGF signalling pathway activator, said BMP signalling pathway inhibitor, and retinoic acid for a second period, wherein said second period is three days ± 24 hours to induce a fundic lineage comprising fundal human gastric organoids (hFGOs) suspended in the basement membrane matrix, and wherein the EGF signalling pathway activator is EGF; c) culturing said hFGOs of step b) with said wnt signalling pathway activator and said EGF signalling pathway activator for a third period that is 11 days ± 24 hours; d) culturing said hFGOs of step c) with said wnt signalling pathway activator, said EGF signalling pathway activator, and FGF 10 for a fourth period that is 10 days ± 24 hours; e) contacting said hFGOs of step d) with the MEK inhibitor PD0325901 for a fifth period, wherein said fifth period is a two day period ± 24 hours to form said gastric fundus tissue comprising a functional fundic cell type. a) contacting an adherent mammalian definitive endoderm cell with a wnt signalling pathway activator, an FGF signalling pathway activator, a BMP signalling pathway inhibitor, and retinoic acid, for a first period; wherein the wnt signalling pathway activator is CHIR99021; the FGF signalling pathway activator is FGF4; and the BMP signalling pathway inhibitor is Noggin; wherein said first period is three days ± 24 hours and wherein said retinoic acid is added for the third day of the first period ± 24 hours to form a three-dimensional posterior foregut spheroid in suspension from said adherent definitive endoderm; wherein the wnt signalling pathway activator is CHIR99021; the FGF signalling pathway activator is FGF4; and the BMP signalling pathway inhibitor is Noggin; wherein said first period is three days ± 24 hours and wherein said retinoic acid is added for the third day of the first period ± 24 hours to form a three-dimensional posterior foregut spheroid in suspension from said adherent definitive endoderm; b) suspending said three-dimensional posterior foregut spheroid in a basement membrane matrix with a growth factor, said wnt signalling pathway activator, an EGF signalling pathway activator, said BMP signalling pathway inhibitor, and retinoic acid for a second period, wherein said second period is three days ± 24 hours to induce a fundic lineage comprising fundal human gastric organoids (hFGOs) suspended in the basement membrane matrix, and wherein the EGF signalling pathway activator is EGF; c) culturing said hFGOs of step b) with said wnt signalling pathway activator and said EGF signalling pathway activator for a third period that is 11 days ± 24 hours; d) culturing said hFGOs of step c) with said wnt signalling pathway activator, said EGF signalling pathway activator, and FGF 10 for a fourth period that is 10 days ± 24 hours; e) contacting said hFGOs of step d) with the MEK inhibitor PD0325901 for a fifth period, wherein said fifth period is a two day period ± 24 hours to form said gastric fundus tissue comprising a functional fundic cell type.