What is the purpose of flaming the lip of the tube?

Flaming the lip of a tube is a technique used in microbiology and other laboratory settings to sterilize the opening of the tube before and after transferring samples. This process helps to eliminate any potential contaminants from the environment that could compromise the integrity of the sample. By passing the lip through a flame, any microbial life present is killed, ensuring that the contents of the tube remain uncontaminated during handling.