CHOCOLATE BARS

I got this puzzle from Lubor Kollar, a group program manager with the Microsoft SQL Server development team. Imagine you have a chocolate bar made up of 40 squares arranged in 5 rows and 8 columns. Your task is to break it into the 40 individual chocolate squares using the minimum number of cuts. You're allowed to make only one cut at a time (not allowed to pile multiple layers or lay them next to each other) and only in straight lines (horizontal or vertical). How many cuts do you need at minimum? Prove your logic; don't just guess.

SOLUTION TO JANUARY'S TABLETS PUZZLE:

Cut each of the remaining four tablets in half. Consume one half of each tablet today and take the rest tomorrow.