Why are women even less represented in engineering than in other STEM? We know that women in much of the developed countries are less represented in STEM studies. However, such a statement hides the fact that women are approx. half of the students in biology, chemistry and maths (check e.g. here ) but barely 20% in engineering. It is often stated that women tend to choose careers where they feel more useful towards society but that is difficult to reconcile with the fact that the share of women in Chemistry is 50% but only 35% in Chemical Engineering, here. I have tried to find sources that would address this difference but in general the topic treated is STEM as a whole.

Are there studies focusing particularly in this difference in gender representation, engineering vs sciences?
I suspect that this is yet another example of the fractal nature of the gender binary. STEM may be coded masculine in general, but within STEM different fields are coded "more masculine" than others.

I'm very familiar with this in my own field: IT in general is masculine, but UI/frontend is more feminine than backend, on the backend system stuff is more masculine than application stuff, writing it in C is more masculine than writing it in ruby, ... This is sometimes even explicitly expressed as "your beard has to be this long to write/understand this code"

I've never found a good explanation for most of these associations, they seem fairly random to me (and apparently change between cultures as well).