A week ago I defrosted and seeded a new vial of human neural stem cells. I have made up the media with appropriate growth supplements and followed the suppliers protocols, changing the media daily. The stem cells are taking longer than anticipated to become 90% confluent. The suppliers protocol says that they should be confluent within 4 - 7 days. Today is day 7 and they are still about 40% confluent. I have no infection in the flask and as I say I have followed the suppliers protocol exactly. Ideas anyone?