Show Data in a GridView Only When a Button is Clicked

I am trying to figure out how to display data in a GridView, only when a button is clicked. 
 
Below is my HTML:
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="DeronPage.aspx.vb" Inherits="DeronPage" %>
 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
 
        <asp:Button ID="Button1" runat="server" Text="Select All Emails!" ...