Yeast. Coloured scanning electron micrograph (SEM) of yeast cells, Saccharomyces cerevisiae, commonly known as Baker's or Brewer's yeast, growing on potato dextrose agar. Yeast is able to ferment sugar, producing alcohol & carbon dioxide in the process. It has long been used in the brewing of beer, the production of wine and in baking of leavened bread (carbon dioxide causes the dough to rise). Medically, dried yeast is used as a source of vitamin B1, riboflavin & nicotinic acid. Yeast divide rapidly by budding off new cells (visible here). They may also reproduce sexually. Magnification: X 430 at 35mm size. Coloured orange. Original is BW print B250/171.