I propose the concept of expressive surfaces as a research theme to investigate and explore aesthetics of computational objects with its emphasis on forms and materials. In this proposal, I describe some of my preliminary studies to illustrate how the concept has been developed to my research theme. Then exploratory examples of expressive surfaces (the sound-sensitive lamp sculpture and the softspiky mouse) are introduced as attempts to specify the theme into a research agenda for computational objects in terms of concept development, prototyping and evaluation. Author Keywords Expressive surfaces, tangible/organic user interfaces, computational objects, aesthetics. ACM Classification Keywords H5.m. Information interfaces and presentation (e.g., HCI): Miscellaneous. General Terms Design