The present invention finds out find out the requirements necessary for preparing a cell condensate in vitro from a large number of cells (several ten thousand to several million cells) and provides a method of forming a cell condensate for self-organization which is capable of realizing complex higher structures (such as liver and kidney) and interactions with other organs.A method of preparing a cell condensate in vitro, comprising culturing a mixture of cells and/or tissues of a desired type in a total cell count of 400,000 or more and 100,000 to 400,000 mesenchymal cells to form a cell condensate of 1 mm or more in size. A cell condensate prepared by the above-described method. A method of preparing a three-dimensional tissue structure, comprising allowing self-organization of a cell condensate prepared by the above-described method to form a three-dimensional tissue structure that has been provided with higher structures. A gel-like support wherein the side on which culture is to be performed has a U- or V-shaped cross-section.
