insert mongodb node.js express

I am trying to add data in my mongodb

models.user.find(function(err, docs){
    console.log(docs)
});

var user = new models.user.model({
    ...
})
user.save();

In a first time console.log well return all what I have in my user collection But when I whant to create my user I have "cannot call method 'model' of undefined"

I don't understand why

Thanks

I find :)

models.user.find(function(err, docs){
console.log(docs)
});

var user = new models.user({
    ...
})
user.save();