See the Light Warning: Attempt to read property "ID" on null in /home/frost/public_html/wp-content/themes/frost-science/content-single.php on line 21 June 18, 2018 /home/frost/public_html/wp-content/themes/frost-science/content-single.php on line 30 https://www.frostscience.org/fun_fact/see-the-light/">By Krystal Guerra, In the deep sea, beyond the reach of sunlight, most animals—upwards of 80%—light up as they travel, hunt and mate.