public static void setUpWrappers() {
        // Map of Opportunity Chatter Posts from Last 7 Days    
        Map<Id,OpportunityFeed> opptyChatter= new Map<Id,OpportunityFeed>([
            SELECT Id, Body, ParentId, CreatedDate, CreatedBy.FirstName, CreatedBy.LastName
            FROM   OpportunityFeed
            WHERE  CreatedDate = LAST_N_DAYS:7
            ORDER BY CreatedDate
        ]);
        
        // Fetch a map of the relevant Opportunities
        Map<Id,Opportunity> opportunityMap = new Map<Id,Opportunity>([
            SELECT Id, Name, AccountId, Account.Name 
            FROM Opportunity 
            WHERE Id IN (SELECT ParentId FROM OpportunityFeed WHERE Id IN :opptyChatter.keySet())
        ]);
        
        // Finally, fetch a map of the relevant Accounts
        Map<Id,Account> accountMap = new Map<Id,Account>([
            SELECT Id, Name
            FROM Account
            WHERE Id IN (SELECT AccountId FROM Opportunity WHERE Id IN :opportunityMap.keySet())
        ]);
        
        // What we want to do is first group these chatter posts by Opportunity
        // So we'll create a map as the following -- key: Opportunity Id -> value: Opportunity Wrapper (which holds the list of respective opportunity chatter posts)
        Map<Id,OpportunityWrapper> oppIdToPosts = new Map<Id,OpportunityWrapper>();
        // Now populate the oppIdToPosts map
        OpportunityWrapper tempOppWrapper;
        for(OpportunityFeed oppChat : opptyChatter.values()) {
            // We'll see if there's an entry in the map for this Opportunity Id
            tempOppWrapper = oppIdToPosts.get(oppChat.ParentId);
            if(tempOppWrapper != null) {
                // If we've already made an entry under this Opportunity Id, then we'll just add to the list of posts
                tempOppWrapper.chatPosts.add(oppChat);
                oppIdToPosts.put(oppChat.ParentId, tempOppWrapper);
            } else {
                // Otherwise, we need to make an initial entry
                tempOppWrapper = new OpportunityWrapper();
                tempOppWrapper.oppRecord = opportunityMap.get(oppChat.ParentId);
                tempOppWrapper.chatPosts = new List<OpportunityFeed>();
                tempOppWrapper.chatPosts.add(oppChat);
                oppIdToPosts.put(oppChat.ParentId, tempOppWrapper);
            }
        }
        
        // In a similar manner, we'll group these Opportunity Wrappers by Account
        Map<Id,AccountWrapper> accIdToOpps = new Map<Id,AccountWrapper>();
        AccountWrapper tempAccWrapper;
        // This time we'll loop through the values of the map we created earlier
        for(OpportunityWrapper oppWrap : oppIdToPosts.values()) {
            // We'll see if there's an entry in the map for this Account Id
            tempAccWrapper = accIdToOpps.get(oppWrap.oppRecord.AccountId);
            if(tempAccWrapper != null) {
                // If we've already made an entry under this Account Id, then we'll just add to the list of opportunity wrappers
                tempAccWrapper.oppWraps.add(oppWrap);
                accIdToOpps.put(oppWrap.oppRecord.AccountId, tempAccWrapper);
            } else {
                // Otherwise, we need to make an initial entry
                tempAccWrapper = new AccountWrapper();
                tempAccWrapper.accRecord = accountMap.get(oppWrap.oppRecord.AccountId);
                tempAccWrapper.oppWraps = new List<OpportunityWrapper>();
                tempAccWrapper.oppWraps.add(oppWrap);
                accIdToOpps.put(oppWrap.oppRecord.AccountId, tempAccWrapper);
            }
        }
        
        // The final map "accIdToOpps" should be finished
        // You can iterate through each AccountWrapper by accessing the values via accIdToOpps.values()
        // Each wrapper will hold the Account record itself, which will hold desired fields via the query made earlier
        // They will also hold a list of OpportunityWrappers, which will hold information about their respective Opportunity and Opportunity Chatter Posts
        
        // Here's an example of looping through each level
        for(AccountWrapper accWrap : accIdToOpps.values()) {
            System.debug(accWrap.accRecord.Name);
            for(OpportunityWrapper innerOppWrap : accWrap.oppWraps) {
                System.debug('--- ' + innerOppWrap.oppRecord.Name);
                for(OpportunityFeed innerOppFeed : innerOppWrap.chatPosts) {
                    System.debug('--- ++ ' + innerOppFeed.Id + ': ' + innerOppFeed.CreatedBy.FirstName);
                }
            }
        }
    }
    
    // Wrapper for a single Opportunity that holds all respective opportunity chatter posts
    public class OpportunityWrapper {
        Opportunity oppRecord {get;set;}
        List<OpportunityFeed> chatPosts {get;set;}
    }
    
    // Wrapper for a single Account that holds all respective opportunities (as wrappers)
    public class AccountWrapper {
        Account accRecord {get;set;}
        List<OpportunityWrapper> oppWraps {get;set;}
    }