When to start reading chapter books to children?

My sister thinks you should start when they are babies to lull them to sleep. Ive been reading picture books to my only just two year old , although sometimes she asks lots of questions and bedtime takes a bit longer I try to repeat the same set of bedtime books to limit this. the longest we reas is the original Paddington.

g At some point though I would like to start the longer form books but not sure at what stage this is appropriate.