An experimental investigation. was conducted to visually observe the boiling behavior in a three-dimensional porous structure made of staggered glass beads, especially the dynamic bubble process and pore-scale liquid flow around bubbles associated with the heat and mass transport taking place at the bubble interface. The experiments show that the dynamic bubble behavior was significantly affected by the bead-packed structure, and several unique boiling phenomena caused by special pore geometry were observed and discussed. The bubble shape and primary bubble interface were described using a force balance acting on the bubble. A theoretical study was performed to describe and evaluate the behavior of the replenished liquid and associated interfacial transport effects. It was concluded from the theoretical analysis that the bubble interface is regulated by interfacial heat and mass transport to provide sufficient driving force for the replenishment. This conclusion is in agreement with the experimental observation. (C) 2004 Elsevier Ltd. All rights reserved.