A filter assembly comprising: a first filter that removes, from a mixed solution of two or more living cells having different sizes and two or more fat-soluble compounds having different sizes, at least a part of the fat-soluble compounds, the first filter comprising a plurality of first through holes that each possess an inner diameter, and at least 90% or more of the first through holes have a hole diameter larger than a largest living cell among the living cells and smaller than a largest fat-soluble compound among the fat-soluble compounds, further comprising: a second filter, the second filter comprising a plurality of second holes, and at least 90% or more of the second holes have a hole diameter larger than a minimum deformation diameter of the living cells and smaller than the inner diameter of the first holes, and has an average linear distance shorter than a maximum inner diameter of the first holes, the minimum deformation diameter is a minimum diameter of a living cell when the cell passes through the hole while being deformed, and the average linear distance is the maximum length of a rod-shaped crystal that passes through the hole, characterized in that said filter assembly further comprises: a third filter, the third filter including third holes each possessing an inner diameter, and at least 90% or more of the third holes have an inner diameter larger than a smallest living cell among the living cells, and larger than a minimum outer diameter of remaining fat-soluble compounds after at least a part of the fat-soluble compounds have been removed by the second filter. a first filter that removes, from a mixed solution of two or more living cells having different sizes and two or more fat-soluble compounds having different sizes, at least a part of the fat-soluble compounds, the first filter comprising a plurality of first through holes that each possess an inner diameter, and at least 90% or more of the first through holes have a hole diameter larger than a largest living cell among the living cells and smaller than a largest fat-soluble compound among the fat-soluble compounds, further comprising: a second filter, the second filter comprising a plurality of second holes, and at least 90% or more of the second holes have a hole diameter larger than a minimum deformation diameter of the living cells and smaller than the inner diameter of the first holes, and has an average linear distance shorter than a maximum inner diameter of the first holes, the minimum deformation diameter is a minimum diameter of a living cell when the cell passes through the hole while being deformed, and the average linear distance is the maximum length of a rod-shaped crystal that passes through the hole, characterized in that said filter assembly further comprises: a third filter, the third filter including third holes each possessing an inner diameter, and at least 90% or more of the third holes have an inner diameter larger than a smallest living cell among the living cells, and larger than a minimum outer diameter of remaining fat-soluble compounds after at least a part of the fat-soluble compounds have been removed by the second filter. a second filter, the second filter comprising a plurality of second holes, and at least 90% or more of the second holes have a hole diameter larger than a minimum deformation diameter of the living cells and smaller than the inner diameter of the first holes, and has an average linear distance shorter than a maximum inner diameter of the first holes, the minimum deformation diameter is a minimum diameter of a living cell when the cell passes through the hole while being deformed, and the average linear distance is the maximum length of a rod-shaped crystal that passes through the hole, characterized in that said filter assembly further comprises: a third filter, the third filter including third holes each possessing an inner diameter, and at least 90% or more of the third holes have an inner diameter larger than a smallest living cell among the living cells, and larger than a minimum outer diameter of remaining fat-soluble compounds after at least a part of the fat-soluble compounds have been removed by the second filter. a third filter, the third filter including third holes each possessing an inner diameter, and at least 90% or more of the third holes have an inner diameter larger than a smallest living cell among the living cells, and larger than a minimum outer diameter of remaining fat-soluble compounds after at least a part of the fat-soluble compounds have been removed by the second filter.