HAML(HTML abstraction  markup language) provides an elegant syntax which is easy to understand, maintain and use.

• It is introduced by Hampton Catlin with its initial release in 2006, it is used for making HTML simpler, easier and cleaner.
• It gives flexibility to have some dynamic content in HTML, PHP, NODE.JS, ASP and in Ruby.
• For running Haml code, file need to be saved with .haml extension.
• The latest version of Haml is rubygem is 4.0.7 and 4.1.0

Source code HAML: 

%html
  %head 
    %title Welcome
  %body
    %h1 Explaination ul li
    %ul
      %li one
      %li two
      %li
        %ol
          %li one
          %li two
      %li three
      %li four
      %ul
        %li five
        %li six
        %li
          %ol
            %li seven
            %li eight
%h1 link Used like this
%h3
  %a{:href => '#', :class => 'bar', :title => 'Bar'}hello haml
  %h1 This is input box
  %input{:type => 'text'}
  %br
  %h1 Button
  %button submit

Source Code LESS:

ul {
  li {
    color: #000;
  }
}
h1{
  color:red
}
 
button{
  color:green;
  padding:2px 50px;
  font-size:18px;
}