Как отсортировать по полю array object?

var schemaMessage = new Schema({
    message: {
        type: String,
        required: true
    },
    from: {
        type: Schema.ObjectId,
        ref: 'User'
    },
    to: {
        type: Schema.ObjectId,
        ref: 'User'
    },
    date_created: {
        type: Date,
        default: Date.now
    }});

var schemaTopic  = new Schema({
    title: {
        type: String,
        required: true
    }
    ,messages: [schemaMessage]   
    ,date_created: {
        type: Date,
        default: Date.now
    }
});