Isolation of stem cells can be a delicate and multistep process whether from blastocytes, somatic tissues, or whole blood. Protocols may also need to be adjusted based on the stem cell source or species. Within this section are products that are useful for stem cell isolation by gradient separation, as with Percoll or Histopaque, as well as isolation by enzymatic digests, as with trypsin and collagenase. The products listed in this section are our most commonly used. Other, more unique products may also be found throughout the Sigma-Aldrich website.