Light microscopy of the unicellular green alga Cylindocystis brebissoni during cooling at a rate of 10°C per minute in the cryoprotective additive dimethylsuphoxide. This image was taken at -10°C and the cells have partitioned into the freeze concentrated solution between ice crystals. For subsequent images click on Next. At this rate of cooling extensive cellular shrinkage is observed and intracellular ice is not apparent.