Any living thing including a plant, animal or fungus can be recorded on iNaturalist.
You can observe all sorts of species - big and small, native and non-native, wild and cultivated.
Please don’t record humans, pets or indoor houseplants.
Remember to observe nature at a variety of locations - backyards, streets, in trees, waterways and under rocks, and in less likely locations such as footpaths and even indoors.
It’s also important to look for species at different times of day. Different species have different habits.