<div class="uk-section uk-section-default uk-flex uk-flex-middle" uk-height-viewport>
    <div class="uk-width-1-1">
        <div class="uk-container uk-text-center">

            <div class="uk-tooltip uk-tooltip-top-center uk-display-inline-block uk-margin-remove uk-position-relative">Tooltip</div>

            <button class="uk-button uk-button-default uk-margin-left" title="Hello World" uk-tooltip>Hover</button>

        </div>
    </div>
</div>