These are two scientists, the one observing is older, more experienced.  She is the one making sure the younger, newer girl is doing what she's supposed to.  The other girl is performing her first experiment in this study.  Before this picture, the older woman explained the procedure to the younger one so now she's just making sure the younger girl is doing as instructed.  The older woman is a little apprehensive to be letting this new woman work on the experiment because she's a little bit of a control freak and likes things to be done a very specific way.  The younger woman is afraid to mess up and is very nervous under the watchful eye of the older one.  The younger woman just wants to do everything correctly to prove she is competent.  Next the older woman is about to pleasantly correct a very tiny, picky thing about the way the younger one is working.
