Neural search, a technique for efficiently searching for similar items in deep embedding space, is the most fundamental technique for handling large multimodal collections. With the advent of powerful technologies such as foundation models and prompt engineering, efficient neural search is becoming increasingly important. For example, multimodal encoders such as CLIP allow us to convert various problems into simple embedding-and-search. Another example is the way to feed information into LLMs; currently, vector search engines are a promising direction. Despite the above attention, it is not obvious how to design a search algorithm for given data. In this tutorial, we will focus on "million-scale search", "billion-scale search", and "query language" to show how to tackle real-world search problems.