We observe the existence of a class of new physical vertex operators in superstring theory, called brane-like states. These operators correspond to physical states with ghost-matter mixing, i.e. they exist at nonzero pictures only. We show that these operators are physical and that they are closely related to non-perturbative dynamics of superstring theory and M-theory, as may be understood to be the emission vertices of extended objects, such as D-branes. We derive the low energy effective action corresponding to these non-perturbative vertex operators and show that this action is given by the DBI expression.