Crude Approach on A Bunch of Weirdo Cells

Cells. (Human cells at least, XD.) Whatever their form has become, they all started from a single cell --  a single cell which came from the fusion of spermie and eggie.

So if you are faced with a slide with a bunch of weirdo cells that you cannot identify, think of their origin.

Zygote matures and, later, forms ectoderm, mesoderm and endoderm.

We can narrow down the possible origin of the weirdo cells by trying to classify them based on germ cells layers or maybe a germ cell .

Ectoderm gives rise to skin, neural tissues and melanocytes.
Mesoderm gives rise to mesenchymal and hematologic cells. 
Endoderm gives rise to epithelial lining (GI and respiratory).