Code Snippet to Bulk Insert Accounts and 5 Contacts to Each Account.
Execute the below script in developer console. It will create 5 Accounts records and each Account have 5 Contacts.
For(integer i=0; i<5; i++) {
Account acc = new Account(Name='Bulk Account '+i, AccountNumber='919102'+i, Rating='Hot');
Insert acc;
For(integer j=0; j<5; j++) {
Contact con = new Contact(LastName=acc.Name +' Contact '+j, AccountId=acc.Id);
Insert con;
}
}