Using a cotton swab, remove cells on upper side of the insert. Make sure you remove all the cells since it is not possible to distinguish between cells on upper or lower side of the insert under the microscope. Cells that have migrated from the upper side of the insert through the pores to the lower side of the insert are counted = cells per microscopic field.

 一般染下层的细胞时会先把上层的细胞擦掉，这样就不存在这个问题了。
如果是想不染色就在可见光下观察，不太好区分，对焦到transwell的小孔平面，看的的细胞一般就是下层的。