細胞や組織を数日から数週間、あるいは数か月にわたって継続的に培養する技術またはその状態を指す。通常の短期培養では観察できない、細胞の成熟、分化、組織構築、機能発現、慢性的な薬剤応答や疾患進行過程の解析を可能にする。

This term refers to the technology or condition of continuously culturing cells or tissues over a period ranging from several days to several weeks or even months. It enables the analysis of cell maturation, differentiation, tissue formation, functional expression, chronic drug responses, and disease progression—phenomena that cannot be observed in typical short-term cultures.