Structuring change history data in MongoDB / NoSQL

I have a Chart on which I need to track changes; the Chart has several properties. A Chart also has a long list of items. So in C#, my Chart object looks like this: public class Chart { public int Id { get; set; } public string Title { get; set; } ... public List Items { get; set; } } Or in JSON, my Chart looks like this (I wrote this JSON by hand, so it could be wrong): { "Id": 1, "Title": "Test Chart", "Items": [ { "Id": 222, "Title": "Test Item", "Price": 112.34 } ] } So my question is as follows: Should I log an entire chart with all the items as a single document, every time there is a change? (Although I read there may be a limit on document size, so this could be a problem.) OR Should I log Chart changes as one type of document and Chart Item changes as a separate type of document? This would allow me to store changes to chart items as a single "line item" document without having to save the entire Chart every time there is a change to a single chart item. OR Is there a better way?