Thank you! Yes, I am using a bunch of different images I found off of google or given to me by the scientist I am working with. To simplify my drawings I break down the image into lights and darks (squinting at a picture helps you see where those lightest and darkest areas are if you aren’t sure). Going in bold and dark in the darkest parts is how I start trying to leave any white areas untouched. From there I’ll color the medium and gradually build on top of that if I need more than one medium tone. To do this I use different sized pens and a variety of lines and cross hatching. Good luck with your illustrations!