Human-type lymphoid tissue organoids, which stably function in our body for a certain period of time or longer, may have a great potential as immune-stimulatory or immune-regulatory devices and could be utilized in the future for the treatment of various diseases such as cancer, severe infection, autoimmunity and congenital as well as acquired immunodeficiency resulting from severe infections or aging. In this review, we discuss about rationality and trials of the synthesis of immunologically functional lymphoid tissue organoids mainly in mouse. We have been recently trying to construct immunologically functioning human-type organoids, and the efforts are also briefly described.