Today we're going to make some more MIV-competent cells. These guys are grown up in supplemented BHI medium (sBHI) (brain-heart infusion of cows! Sounds like the witches from Macbeth :S) until they reach a certain density, then they're put in MIV starvation medium (not as nutritious as the sBHI) for 100 minutes. After that time, they're considered "competent", or able to take up DNA by themselves. Then they're put into the freezer for later use.