Provided is a technique for efficiently aggregating macromolecules such as ECM together with cells. A method for creating a cell or a cell aggregate loaded with macromolecules, the method comprising adding, to a medium containing a swellable material, a solution containing macromolecules and at least one cell to aggregate the macromolecules together with the cell. A method for controlling the function and/or the property of a cell or a cell aggregate, the method comprising culturing the cell or the cell aggregate loaded with the macromolecules created in the aforementioned method. A method for culturing a cell or a cell aggregate, the method comprising: adding, to a medium containing a swellable material, a solution containing macromolecules and at least one cell to aggregate the macromolecules together with the cell and to produce a macromolecule capsule encapsulating the cell or the cell aggregate and culturing the cell or the cell aggregate in the capsule. For preparing a three-dimensional cell tissue, methods such as 96-well U-bottom plating and hanging drop technique are conventionally used. In the methods of the present invention, 2000 cells are mixed with 1 μl of the medium containing ECM, and the ECM and cells can be simultaneously aggregated. If the efficiency here is defined as 1, a calculation can be made that, when 96-well U-bottom plating or hanging drop technique is used, ECM can only be mixed in the three-dimensional cell tissue at an efficiency of about 1/12000 or about 1/2400, respectively. Thus, with the present invention, the cost for ECM can be reduced to about one several-thousandth to one hundred-thousandth, and it becomes possible to effectively use artificial ECM that cannot be synthesized in large quantity or rare ECM that can be extracted only at a very small amount because of reasons such as the subject being a small living organism.
