You Don't Need JavaScript for That!

tooltip.md

<span class="tooltip-toggle" data-tooltip="Sample text for your tooltip!">
  Label for your tooltip
</span>

.tooltip-toggle {
  cursor: pointer;
  position: relative;

  //Tooltip text container - above element
  //You can adjust the position to make the container appear below or beside the element
  &::before {
    background-color: #000;
    border-radius: 5px;
    color: #fff;
    content: attr(data-tooltip); //This pulls in the text from the element with the tooltip
    left: -80px; //This centers the container above the element
    padding: 1rem;
    position: absolute;
    text-transform: none;
    top: -80px; //This places the container above the element that needs a tooltip
    transition: all 0.5s ease;
    width: 160px;
  }

  //Tooltip arrow
  //You can adjust the position of this to align nicely with the element that
  //needs a tooltip. You can also use `transform` to rotate it to make the
  //tooltip work below or next to the element.
  &::after {
    border-left: 5px solid transparent;
    border-right: 5px solid transparent;
    border-top: 5px solid #000;
    content: " ";
    font-size: 0;
    left: 9px; //This centers the arrow above the element with the tooltip
    line-height: 0;
    margin-left: -5px;
    position: absolute;
    top: -12px; //This positions the arrow at the bottom of the container
    width: 0;
  }

  //Setting up the transition
  &::before,
  &::after {
    opacity: 0;
    pointer-events: none;
  }

  //Triggering the transition
  &:hover::before,
  &:hover::after {
    opacity: 1;
    transition: all 0.75s ease;
  }
}

Dropdown menu

<div class="nav-container">
  <ul class="nav-items">
    <!-- Navigation -->
    <li class="nav-item"><a href="#">Home</a></li>
    <li class="nav-item"><a href="#">About</a></li>
    <li class="nav-item"><a href="#">Contact</a></li>

    <!-- Dropdown menu -->
    <li class="nav-item nav-item-dropdown">
      <a class="dropdown-trigger" href="#">Settings</a>
      <ul class="dropdown-menu">
        <li class="dropdown-menu-item">
          <a href="#">Dropdown Item 1</a>
        </li>
        <li class="dropdown-menu-item">
          <a href="#">Dropdown Item 2</a>
        </li>
        <li class="dropdown-menu-item">
          <a href="#">Dropdown Item 3</a>
        </li>
      </ul>
    </li>
  </ul>
</div>

//Nav bar styling
.nav-container {
  background-color: #fff;
  display: block;
  margin: 0 auto;
  max-width: 400px;
  padding: 1em;
  text-align: center;
}

ul,
li {
  list-style: none;
  -webkit-padding-start: 0;
}

//Navigation menu
.nav-item {
  display: inline;
  padding: 1em;
}

//Dropdown menu
.nav-item-dropdown {
  position: relative;

  &:hover > .dropdown-menu {
    display: block;
    opacity: 1;
  }
}

.dropdown-trigger {
  position: relative;

  &:focus + .dropdown-menu {
    display: block;
    opacity: 1;
  }

  &::after {
    color: #ED3E44;
    content: "›";
    font-size: 24px;
    font-weight: bold;
    position: absolute;
    right: -15px;
    top: -5px;
    transform: rotate(90deg);
  }
}

.dropdown-menu {
  background-color: #fff;
  display: inline-block;
  display: none;
  opacity: 0;
  position: absolute;
  right: -10px;
  text-align: right;
  top: 2.5rem;
  transition: opacity 0.5s ease;
  width: 160px;
}

.dropdown-menu-item {
  cursor: pointer;
  padding: 1em;
  text-align: center;

  &:hover {
    background-color: #ccc;
  }

Toggle Visibility

<div class="toggle">
  <!-- Checkbox toggle -->
  <input type="checkbox" value="selected" id="beethoven-joke" class="toggle-input">
  <label for="beethoven-joke" class="toggle-label">What was Beethoven's favorite fruit?</label> 

  <!-- Content to toggle -->
  <div role="toggle" class="toggle-content">
    BA-NA-NA-NA!
 </div>
</div>

.toggle {
  margin: 0 auto;
  max-width: 400px;
}

//Style toggle
.toggle-label {
  background: #fff;
  cursor: pointer;
  display: block;
  font-size: 16px;
  margin: 0 auto 1em;
  padding: 1em;

  &:after {
    content: "+";
    float: right;
  }
}

//Style content
.toggle-content {
  padding: 1em;
}

.toggle-input {
  display: none; //Hide input element

  &:not(checked) ~ .toggle-content {
    display: none; //Hide content
  }
}

//Display content when checkbox is "checked"
.toggle-input:checked {
  ~ .toggle-content {
    display: block;
  }

  ~ .toggle-label {
    &:after {
      content: "-"; //Change label's '+' to '-' when checked
    }
  }
}