system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When getting a flu shot, how does the needle go in?

Does it go into the space between cells, does it break cells on its way in, or some combination of the two? I am having a difficult time visualizing how it works.
gpt
A combination of the two would be appropriate. The 'space' between cells is comprised of the Extracellular Matrix, which is a bunch of proteins that link the two. The needle goes through whatever's in its way.