It looks like the picture from this post from recently where they said it's probably spittlebug foam. But I'm posting mine as well because I don't think that the answers that OP got could be the solution in my case. We have bug nets at the windows and the last time I opened them in my room was 12 hours ago. I also looked around for a bug but I can't find anything. It definitely wasn't there 12 hours ago; I went to the bathroom for a few minutes and I noticed it when I came back. The foam went away after a few minutes. I do have a cat but I really don't think it was her (she wouldn't just jump on my nightstand and drool there and leave, in fact she's never even been sitting on the nightstand). My brother is at home but it can't have been him, and it's virtually impossible that someone else went into the apartment (I also would have heard someone walking because we have linoleum). There are no snail trails and like I said, I didn't find any animals. There are also no birds or bats. Could it be some really small bugs like bed bugs?