The video shows the yeast Saccharomyces cerevisiae growing in a complete medium containing 0.5% (wt/vol) agar. The cells, which are 5 to 10 µm in diameter, were harvested from an exponentially growing shake flask culture. The video frames were recorded at intervals of 30 s and have been numbered. This information can be used to determine the doubling time of the culture, simply by recording the time taken by the cells to pass from a discrete stage of one generation to the equivalent stage of the next generation. Performing this exercise provides an alternative to the use of shake flask cultures in teaching. The age of the culture was 2 h at the start of the video.