Abstract: Cells and tissues, in particular sensitive cells and tissues, such as oocytes, fertilized oocytes and preimplantation embryos, which require highly stable physical and chemical environment for in vitro development, are cultured in closed containers submerged or immersed in thermostatically controlled liquid baths, the containers being provided with an appropriate inner atmosphere containing, e.g. carbondioxide, oxygen and humidity in appropriate levels. The incubator containers may e.g. be gas and liquid impervious, flexible, sealable, preferably transparent bags which after sealing are submerged or immersed directly in the thermostatically controlled liquid bath. The liquid in the bath is preferably water. An incubator for submerse or immerse culture of cells and tissues in the above manner is also described. Also a transportable liquid incubator for culturing cells and tissues in the field is described.