We are interested in the role that aerosol particles play in both liquid water (i.e. acting as cloud condensation nuclei, or CCN) and ice cloud formation (i.e. acting as ice nuclei, IN). Recent projects in this area involve field measurements of both the CCN and IN numbers in a coastal setting on the west coast of Vancouver Island. The questions we are investigating, now also in the lab, are the roles that particles from the organic microlayer present on the surface of the ocean may play as CCN and IN. As well, we have continuing projects on the nature of deposition nucleation (i.e. condensation from the gas to the particles to form ice) that occurs in the atmosphere on a wide range of substrates. These measurements are made with both home-built and commercial diffusion cloud chambers.