Wyeast Labs was formed in Hood River, Oregon in 1986 and has been providing a wide range of quality, reliable strains ever since. They package their 100 billion cell count strains in their infamous "smack pack" which contains a small pouch of nutrients that you pop in preparation for your brew day. This will introduce those nutrients into your yeast strain and initiate a swelling of your yeast pouch. We've noticed that certain strains tend to swell more and faster than others, so do not be too worried if the swelling doesn't take off right away. We've also encountered their pouches slightly swelling prior to popping the smack pack. This should not be too alarming unless the package seems like it's completely swollen and about to burst. Wyeast typically attributes some slight pre-swelling to trace levels of fermentable carbohydrates or CO2 in yeast slurries at the time of packaging may cause a slight expansion as a result of off-gassing. This is simply a small amount of metabolism or CO2 being released from the media and can even occur with proper storage.