We consider the bubbles of quark matter which survived the confinement phase transition in the universe at high temperature. With the constraint of being neutral and of conservation of baryonic number, we obtain the evolution of the density of quarks of different flavours and of pressure till their contraction stops. On the other hand we find that at low temperature and increasing pressure, a system of ordinary quarks chooses to acquire a strange component. This is what might happen in neutron stars becoming sources of strangelets. © 2003 American Institute of Physics