The example used for this question will be a Medline search on Ovid, but the principle applies to most subject searching databases that we subscribe to.

The first image attached at the bottom of this page, 'MeSH headings', shows you the entire structure of terms indexed under 'Education'. If we look at it closely we will see that only 20665 articles are indexed under 'Education'. However, the same heading has a lot of other narrower terms, many of them, such as Curriculum, with their own narrower terms; Competency-Based Education, Interdisciplinary Studies, Education Mainstreaming and Problem-Based Learning.

Will exploding 'Education' automatically include the 74106 articles under Curriculum, but also 3903 articles in Competency-Based Education, 1051 in Education Mainstreaming and so on?

The answer is 'Yes'. As you can see in the second image attachment 'Results' there are three searches for Education:

• In the first one we only ticked the box on the left of the term, so we did not explode it;
• The second search shows you that we exploded the same term but made no other selections. This retrieved 796923 articles.
• In the third search we exploded 'Education' again in the same way, but also exploded 'Curriculum' underneath, by ticking the box on its left along with the one for exploding. The number of results was identical.

As long as you are happy to include all the terms within a broader MeSH heading, exploding it will do that job for you. You would probably go through the terms individually if there were many of them and some of them were definitely irrelevant to your search. This would reduce the number of articles you are screening, but it is a choice you have to make.