Significance is not related to size: meeting a few virus particles [1] could be the most significant - and possibly last - event of notice in your life. On the other hand few people will be aware of meeting the largest - and possibly oldest - organism on the planet when they look at a honey mushroom in Oregon National Forest [2].

[1] https://en.wikipedia.org/wiki/Ebola_virus

[2] http://www.nationalgeographic.com.au/nature/the-worlds-large...