Step in dog poo Step on a rusty nail Soft object ie water = step in. Step in to the bath. You can't walk on water. Hard object = step on. You can then stand on it if you wish. I hope that answers your question. If you'd like to practice speaking, I'd be happy to help you develop a study plan. Feel free to look at my teaching profile and class offerings and send me a message if you think I can help you.

That depends if you are stepping on something or stepping in something. You can use either for certain situations. You can't say you stepped in a nail..