ooh!
the thing i think i'm currently fixated on lately is either sealife or all the different Vocaloids/UTAUloids that exist.
sealife as in - jellyfish, coral, algae, unicellular sealife, and hydrothermal vents.
but also Vocaloids/UTAUloids as in all the various ones that were released in the 2000s-2010s - like Fukase, Rana, Macne Nana & Macne Petite, and Megurine Luka
or space, if i feel like it. usually it depends on the time of day i'm fixated lol
for instance, when i was waking up this morning (and this was the same for every few days ago too), i couldn't stop talking about the different Vocaloid/UTAUloid's personalities and what they'd be like to interact with, for some reason. i dunno, but thinking Gakupo could kill you easily is pretty funny to me still.
usually if it's during the middle of the day, sealife is what i like focusing on - and same as well when i'm going to bed.
i like phytoplankton, jellyfish/comb jellies, bioluminescence, and even those weird unicellular organisms -
like this one!at night (and twilight usually), i fixate on space. while my city doesn't have the best night sky, i always feel it's really interesting looking through nebulae, white dwarfs, dwarf planets, trojans, asteroids, greeks, and other things too (^_^)