After chromosomes are formed, during which phase of mitosis do the chromosomes attach to the spindle fibers by their centromeres?

Spindle fibers are attached to their centromeres in metaphase.

Chromosomes are formed during the prophase of mitosis, in this phase nucleus disappears, formation of spindle fiber takes place and chromosomes are formed from the condensed DNA which is then followed by the alignment of spindle fibers on the equator of the cell to get attached with their centromeres, alignment followed by the attachment of spindle fibers to their centromeres occurs in metaphase.  

the "power" of a lens is its resolution power, or its ability to distinguish between to closely located points. with the low power lens, it is likely you will see the rough form of the hay and maybe some movement of dots around the hay. however, when observed with the high power lens, the detailed features of the hay become visible and the microbes being grown are more clearly visible.

i hope this you

geologic time scale (for gradpoint) =)