Sometimes when I behold a certain body part, even though it seems simple enough, the fact is that you have to draw the shape around it sometimes in order to get it right. If you notice with mouths, they are surrounded by muscle and just skin. This may sound redundant, but I found today that if I draw a circle around the intended mouth, then I can mirror the shape inside and it will look right.
I especially like the one of the infant, the other one in pen was to just see how I could line things. Also, I liked how the placement of the chin muscles would work as well.
I started today also drawing young women. Every person has a stage in life where the look differs, but the person is still recognizable. Plus, I wanted to get the expressions down as well. The eyes were kind of my bane as well.
Another challenging aspect is faceted gemstones. You may think that they are all geometric and such, but to be honest, there are two things complicating it. Both of them pretain to the aspect that the item itself is faceted. First of all, you have to see how the colors bend and such, and sometimes the discernable pattern is not really there. Secondly, they're faceted and displayed as such to show bright points. But oh my lord, what bright points they are, plus varying other colors, AND you got to keep them crisp.
Aye yi yi. My brain is so tired. XD