Experimentally

The natural scientific method essentially consists not of verification, but falsification: a model is valid as long as it cannot be experimentally refuted.

Komarova notes that everyone who studies cancer knows that genetic instability (and the mutations it causes) are important for cancer cells: cancer couldn't spread without it. It's not so clear why this mutation rate slows down in later stages of the tumor. She says that this has been observed experimentally, but researchers can't decide whether it's important for cancer growth or if it's just a side-effect of cancer.

Gut feelings play a role in science; they are called hypotheses, and then they are verified or disproven experimentally.

The end of the 20th century and the start of the new millennium have bore witness to a remarkable revolution in the way parasite/host biological interactions can be conceptually designed and experimentally studied.

However, before most of this was experimentally and observationally discovered, they were perhaps best known for their “almost unique” ability to squirt ink when harangued, creating a smokescreen before jetting off to safety.