Cell culture media is the liquid that we grow cells in and functions to provide all the nutrients the cells need. The base media has sugars and amino acids as a base and then you can add any additional nutrients that are more specific to your cell type. The media is typically red, which is due to the presence of a pH indicator so that us scientists can know the pH of the media just by looking at it. When cells consume the media, they also release metabolic waste which makes the media acidic so it will turn yellow. We can use this as an indicator that it's time to change the media – meaning we remove the old media and add fresh media. So overall media is basically the food for your cells, and we replace it every other day usually to make sure the cells always have enough fresh “food”.