Well, for one thing, they ensure that a scientist can't claim a certain result, which might be biased and thus inaccurate, because he or she is being paid by, say, big business interests. For another, they ensure that medicines or treatments can't be made available to the public without thorough testing, replication, and peer review.
The light intensity. The transparency of the filter, the bandwidth of the filter,
Also the color temperature of light source
This is what a chromosome looks like during mataphase
