I'm not sure if its just me, but I had never heard of these before! My 8 week old has gone from a happy baby to grumpy and clingy starting at exactly 8 weeks. While I thought it was from her shots, I googled it and apparently its a wonder week! Symtoms include clininess, crying and fussiness. Its a developmental stage. Haooens at 5 week, 8 weeks, 12 weeks, 19 weeks and so on. Has anyone noticed a change in their Lo during these times? It can last a few days up to 14.