Detailed analyses of cambium activity and wood formation during growth need repeated sampling of newly formed xylem. In order to be minimally invasive, wood samples are extracted as microcores. Despite the research done on xylem cell development and the increasing interest in intra-annual studies of xylogenesis, few tools are available for microcore sampling. Methods originally designed for other purposes have often been used, but no details are available on their efficiency and usefulness. Information is also lacking on laboratory preparation techniques for cell analysis of tree-ring formation, leading to difficulties in carrying out these experiments. The advantages and limits of the tools used up to now are described. A new tool, named Trephor (patent pending n° PD2004A000324), specifically designed for long-lasting use is presented. Trephor is chisel-shaped for a fast recovery of 2 mm diameter microcores. The cutting tube is inserted into the wood using a hammer and no other accessory is required. Simple technical characteristics allow high quality samples to be collected from both softwood and hardwood species with minimum damage to the sampled trees. Trephor was tested during the 2004 growing season, demonstrating good resistance to wear and tear and mechanical stress. Embedding the microcores in paraffin for fast section preparation is described.