Genetic Engineering is very useful for making large amounts of useful biological substances such as hormones from living organisms such as bacteria. You can visit the following websites to learn more about genetic engineering:

Websites:

http://www.madehow.com/Volume-7/Insulin.html

http://www.bbc.co.uk/schools/gcsebitesize/science/triple_ocr_gateway/beyond_the_microscope/gene_technology/revision/1/

http://www.abpischools.org.uk/page/modules/diabetes/diabetes6.cfm?coSiteNavigation_allTopic=1