Thank you very much for your comment! The inner diameter (ID) of the biopsy pipette used in this video was 20µm (e.g. Ref. 15112 or 15602) because it is a mouse embryo. For human embryos, an ID of 25µm is normally used. You can find on our website the different options we have available for biopsy pipettes: www.vitrolife.com/products/micromanipulation-pipettes/biopsy-pipettes/ If you need a contact person in your region, just let us know. You can also use the contact form via our website. As for your question about the number of cells, usually 4-6 cells are OK.