var bubbles = document.getElementById('bubbles')

​

for (var i = 1, len = 7; i <= len; i++) {

  // This is the cell

  var bubble = document.createElement('div')

  // This is the div in the cell

  var boob = document.createElement('div')

  bubble.classList.add('bubble')

  boob.classList.add('boob')

  // We put the div in the cell

  bubble.appendChild(boob)

  // And the cell in the table

  bubbles.appendChild(bubble)

}