The Thornton Memorial Lecture will discuss atomic layer deposition (ALD) highlights from the last 25 years. The lecture will trace the history of ALD starting with the earlier developments in atomic layer epitaxy (ALE). The presentation will recount the importance of semiconductor processing needs to the growth of ALD and the situation that led to the name change from ALE to ALD. The talk will also describe personal highlights in the development of ALD and acknowledge some of the people and circumstances behind those developments. In addition, the lecture will include commentary on the evolution of ALD. The presentation will conclude by looking ahead to the future of ALD.