From our perspective to the largest scale measured, and then to the smallest scale measurable. This video illustrates the effect of adding or subtracting another zero on a given scale. The largest distance measurable in the observable universe was calculated to be about 47 billion lightyears; about 4.4 \times 10^{10} \mbox{ m}. The smallest scale measurable, or at least defined to my knowledge, is the Planck length; \ell_\text{P} \approx 1.6 \times 10^{-35} \mbox{ m}. One nucleotide (the molecules that are the building blocks of DNA) measures about 0.33 nm. Stretched out, human chromosome 1, with its approximately 249 million nucleotides, would be about 8 cm long. The whole human genome would be about 3 m in length. Not much compared to galactic distances, but still quite interesting.