In 1996, Greiner created and patented a plastic earring organizer, which was picked up by J. C. Penney before the holiday season. She took out a $300,000 loan to make this product and paid it back in eighteen months. She has also patented consumer products in other categories including cosmetic organization, jewelry storage, travel, electronics, and household items. She is also known venture in capital investing, product design consulting and television production.
Greiner started her own company after her J.C.Penney success and her product began appearing on Home Shopping Network and in the retail store, Bed, Bath and Beyond. Shortly thereafter, she transitioned to QVC and in 2000, landed her own show called Clever & Unique Creations, which is one of the longest running show on the network.
In 2012, Greiner joined the US TV series Shark Tank. In 2014, her investment in Scrub Daddy, a company that produces a texture changing household sponge, was noted as one of the biggest success story in Shark Tank history. On July 30, 2014, she sold more than 2 million sponges on QVC (in one day alone).
Another Shark Tank investment by Greiner made in Bantam Bagels (mini stuffed bagels) in 2014, was fully acquired by T. Marzetti Company, a subsidiary of Lancaster Colony Corporation. Other investments by Greiner include Squatty Potty, Readerest, Paint Brush Cover, Hold Your Haunches, Drop Stop, FiberFix, Simply Fit Board, Sleep Styler and Screenmend.