Officeial site:

http://www.tinymce.com/index.php

Example (With Responsive Filemanager):

<!-- TinyMCE -->
<script src="<?= base_url() ?>assets/admin/plugins/tinymce/tinymce.min.js"></script>

tinymce.init({
	selector: "textarea.tinymce", 
	plugins: [
	 "advlist autolink link image lists charmap print preview hr anchor pagebreak spellchecker",
	 "searchreplace wordcount visualblocks visualchars code fullscreen insertdatetime media nonbreaking",
	 "save table contextmenu directionality emoticons template paste textcolor responsivefilemanager"
	], 
	toolbar: "insertfile undo redo | styleselect | bold italic | alignleft aligncenter alignright alignjustify | bullist numlist outdent indent | link image | print preview media fullpage | forecolor backcolor responsivefilemanager", 
	external_filemanager_path:"/assets/admin/plugins/filemanager/",
	filemanager_title:"Responsive Filemanager" ,
	external_plugins: { 
		"filemanager" : "plugins/responsivefilemanager/plugin.min.js"
	}
});

Notes:

1. When using AJAX to submit a form, this line is required before submitting the form:
   tinyMCE.triggerSave();