<label for="name">Product name:</label>
<input id="name" name="name" type="text" value="Shampoo" minlength="3" maxlength="20" required />

<label for="description">Product description:</label>
<textarea id="description" name="description" minlength="10" maxlength="40" required></textarea>

label {
  display: block;
  margin-top: 1em;
}

input:valid,
textarea:valid {
  background-color: palegreen;
}