Nonequilibrium cold plasmas at atmospheric pressure are an ideal solution for treatment of an assortment of samples that cannot endure vacuum such as biological and medical materials. These kinds of plasmas contain molecular and atomic species that play a key role in modification of biological tissues and triggering of biological response. Accordingly, one needs to identify the species and determine their behaviour and concentration and to understand the mechanisms that bring these species to the surface of the sample. Here we will show results of the time-resolved mass spectrometry that provides us with information on composition and mechanisms within plasma.