It's difficult to definitively say which tissue is the most complex in the human body, as complexity can be subjective and depends on how you define it. Different tissues have different levels of complexity based on:

* Cellular diversity: Some tissues contain many different types of cells, while others are relatively homogeneous.

* Intercellular connections: The intricate network of connections between cells within a tissue can contribute to its complexity.

* Functional complexity: Tissues can perform very specific and complex functions, requiring specialized structures and processes.

However, some tissues are often considered contenders for being among the most complex:

* Brain tissue: The brain is arguably the most complex organ in the body, and its tissue is incredibly diverse. It contains billions of neurons with intricate connections, supporting a vast array of functions including thought, memory, emotion, and sensory processing.

* Immune tissue: The immune system is a complex network of cells and tissues that work together to defend the body against infection and disease. This system utilizes a diverse array of cells, each with specialized functions, and involves a complex web of interactions.

* Skin tissue: While often thought of as a simple barrier, skin is actually a complex organ with multiple layers and diverse cell types. It plays a crucial role in protecting the body, regulating temperature, and sensing the environment.

Ultimately, the answer to what's the "most complex" tissue depends on your criteria for complexity. It's a fascinating question that highlights the incredible intricacy and adaptability of the human body!