diff --git a/assets/css/main.css b/assets/css/main.css
index 8162397..f68a4c9 100644
--- a/assets/css/main.css
+++ b/assets/css/main.css
@@ -15,6 +15,7 @@
 @import url('./floating-elements.css');
 @import url('./stats.css');
 @import url('./comparison.css');
+@import url('./metadata.css');
 
 /* Responsive design */
 @import url('./responsive.css');
diff --git a/assets/css/metadata.css b/assets/css/metadata.css
new file mode 100644
index 0000000..872fef6
--- /dev/null
+++ b/assets/css/metadata.css
@@ -0,0 +1,180 @@
+/* ========================================
+   METADATA POPUP STYLES
+   ======================================== */
+
+/* Metadata button on thumbnails */
+.metadata-btn {
+    position: absolute;
+    top: 8px;
+    right: 8px;
+    background: rgba(0, 0, 0, 0.7);
+    color: white;
+    border: none;
+    border-radius: 50%;
+    width: 32px;
+    height: 32px;
+    font-size: 16px;
+    cursor: pointer;
+    z-index: 10;
+    transition: all 0.2s ease;
+    backdrop-filter: blur(4px);
+    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
+    opacity: 0;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    line-height: 1;
+}
+
+.grid-item:hover .metadata-btn {
+    opacity: 1;
+}
+
+.metadata-btn:hover {
+    background: rgba(0, 0, 0, 0.9);
+    transform: scale(1.1);
+    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
+}
+
+.metadata-btn:active {
+    transform: scale(0.95);
+}
+
+/* Grid item positioning for metadata button */
+.grid-item {
+    position: relative;
+}
+
+/* Metadata popup */
+.metadata-popup {
+    background: var(--card-background);
+    border: 1px solid var(--border-color);
+    border-radius: 8px;
+    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
+    max-width: 320px;
+    min-width: 250px;
+    opacity: 0;
+    transform: translateY(-10px);
+    transition: all 0.2s ease;
+    backdrop-filter: blur(10px);
+    z-index: 1000;
+}
+
+.metadata-popup.show {
+    opacity: 1;
+    transform: translateY(0);
+}
+
+.metadata-popup-header {
+    padding: 12px 16px;
+    border-bottom: 1px solid var(--border-color);
+    background: var(--header-background);
+    border-radius: 8px 8px 0 0;
+}
+
+.metadata-popup-header h4 {
+    margin: 0;
+    font-size: 14px;
+    font-weight: 600;
+    color: var(--text-color);
+    word-break: break-word;
+}
+
+.metadata-popup-content {
+    padding: 12px 16px;
+    max-height: 300px;
+    overflow-y: auto;
+}
+
+.metadata-field {
+    display: flex;
+    margin-bottom: 8px;
+    gap: 8px;
+    align-items: flex-start;
+}
+
+.metadata-field:last-child {
+    margin-bottom: 0;
+}
+
+.metadata-key {
+    font-weight: 500;
+    color: var(--accent-color);
+    font-size: 12px;
+    min-width: 80px;
+    flex-shrink: 0;
+}
+
+.metadata-value {
+    font-size: 12px;
+    color: var(--text-color);
+    word-break: break-word;
+    flex: 1;
+}
+
+.metadata-value code {
+    background: var(--code-background);
+    padding: 2px 4px;
+    border-radius: 3px;
+    font-size: 11px;
+    font-family: 'Courier New', monospace;
+}
+
+.metadata-tag {
+    background: var(--accent-color);
+    color: var(--background-color);
+    padding: 2px 6px;
+    border-radius: 12px;
+    font-size: 10px;
+    font-weight: 500;
+    margin-right: 4px;
+    display: inline-block;
+}
+
+.metadata-more {
+    color: var(--breadcrumb-color);
+    font-style: italic;
+    font-size: 11px;
+}
+
+.no-metadata {
+    color: var(--breadcrumb-color);
+    font-style: italic;
+    margin: 0;
+    text-align: center;
+    padding: 20px 0;
+}
+
+/* Custom scrollbar for metadata popup */
+.metadata-popup-content::-webkit-scrollbar {
+    width: 6px;
+}
+
+.metadata-popup-content::-webkit-scrollbar-track {
+    background: transparent;
+}
+
+.metadata-popup-content::-webkit-scrollbar-thumb {
+    background: var(--border-color);
+    border-radius: 3px;
+}
+
+.metadata-popup-content::-webkit-scrollbar-thumb:hover {
+    background: var(--accent-color);
+}
+
+/* Responsive adjustments */
+@media (max-width: 768px) {
+    .metadata-popup {
+        max-width: calc(100vw - 32px);
+        min-width: 200px;
+    }
+    
+    .metadata-btn {
+        width: 28px;
+        height: 28px;
+        font-size: 14px;
+        top: 6px;
+        right: 6px;
+    }
+}
diff --git a/assets/js/metadata-popup.js b/assets/js/metadata-popup.js
new file mode 100644
index 0000000..085c3a9
--- /dev/null
+++ b/assets/js/metadata-popup.js
@@ -0,0 +1,212 @@
+/**
+ * Metadata Popup functionality for Gallery
+ * 
+ * Handles showing metadata in small popups overlaid on plot thumbnails
+ */
+
+class MetadataPopup {
+    constructor() {
+        this.activePopup = null;
+        this.init();
+    }
+
+    init() {
+        // Close popup when clicking outside
+        document.addEventListener('click', (e) => {
+            if (!e.target.closest('.metadata-btn') && !e.target.closest('.metadata-popup')) {
+                this.hidePopup();
+            }
+        });
+
+        // Close popup on Escape key
+        document.addEventListener('keydown', (e) => {
+            if (e.key === 'Escape') {
+                this.hidePopup();
+            }
+        });
+    }
+
+    showPopup(button, plotName, metadata) {
+        // Hide any existing popup
+        this.hidePopup();
+
+        // Create popup element
+        const popup = document.createElement('div');
+        popup.className = 'metadata-popup';
+        popup.innerHTML = this.formatMetadata(plotName, metadata);
+
+        // Position popup relative to button
+        const rect = button.getBoundingClientRect();
+        popup.style.position = 'fixed';
+        popup.style.left = rect.left + 'px';
+        popup.style.top = (rect.bottom + 5) + 'px';
+        popup.style.zIndex = '1000';
+
+        // Add to DOM
+        document.body.appendChild(popup);
+        this.activePopup = popup;
+
+        // Adjust position if popup goes off screen
+        setTimeout(() => {
+            const popupRect = popup.getBoundingClientRect();
+            
+            // Adjust horizontal position
+            if (popupRect.right > window.innerWidth) {
+                popup.style.left = (rect.right - popupRect.width) + 'px';
+            }
+            
+            // Adjust vertical position
+            if (popupRect.bottom > window.innerHeight) {
+                popup.style.top = (rect.top - popupRect.height - 5) + 'px';
+            }
+        }, 0);
+
+        // Animate in
+        requestAnimationFrame(() => {
+            popup.classList.add('show');
+        });
+    }
+
+    hidePopup() {
+        if (this.activePopup) {
+            this.activePopup.classList.remove('show');
+            setTimeout(() => {
+                if (this.activePopup && this.activePopup.parentNode) {
+                    this.activePopup.parentNode.removeChild(this.activePopup);
+                }
+                this.activePopup = null;
+            }, 200);
+        }
+    }
+
+    formatMetadata(plotName, metadata) {
+        if (!metadata || Object.keys(metadata).length === 0) {
+            return `
+                <div class="metadata-popup-header">
+                    <h4>${plotName}</h4>
+                </div>
+                <div class="metadata-popup-content">
+                    <p class="no-metadata">No metadata available</p>
+                </div>
+            `;
+        }
+
+        let html = `
+            <div class="metadata-popup-header">
+                <h4>${plotName}</h4>
+            </div>
+            <div class="metadata-popup-content">
+        `;
+
+        // Show priority fields first
+        const priorityFields = ['title', 'description', 'plot_type', 'experiment'];
+        const processedKeys = new Set();
+        
+        // Display priority fields first
+        for (const key of priorityFields) {
+            if (metadata[key] !== undefined) {
+                html += this.formatMetadataField(key, metadata[key]);
+                processedKeys.add(key);
+            }
+        }
+
+        // Show file info if available
+        if (metadata.file_info) {
+            html += `<div class="metadata-section-title">File Information</div>`;
+            html += this.formatMetadataField('File Size', metadata.file_info.size);
+            if (metadata.file_info.extension) {
+                html += this.formatMetadataField('Format', metadata.file_info.extension);
+            }
+            processedKeys.add('file_info');
+        }
+
+        // Show timestamps if available
+        if (metadata.timestamps) {
+            html += `<div class="metadata-section-title">Timestamps</div>`;
+            if (metadata.timestamps.created_human) {
+                html += this.formatMetadataField('Created', metadata.timestamps.created_human);
+            }
+            if (metadata.timestamps.modified_human) {
+                html += this.formatMetadataField('Modified', metadata.timestamps.modified_human);
+            }
+            processedKeys.add('timestamps');
+        }
+
+        // Show extracted info if available
+        if (metadata.extracted_info && Object.keys(metadata.extracted_info).length > 0) {
+            html += `<div class="metadata-section-title">Plot Details</div>`;
+            for (const [key, value] of Object.entries(metadata.extracted_info)) {
+                html += this.formatMetadataField(key, value);
+            }
+            processedKeys.add('extracted_info');
+        }
+
+        // Display other fields (excluding generation info unless it's the only data)
+        const otherKeys = Object.keys(metadata).filter(key => 
+            !processedKeys.has(key) && key !== 'generation'
+        );
+        
+        if (otherKeys.length > 0) {
+            html += `<div class="metadata-section-title">Additional Information</div>`;
+            for (const key of otherKeys) {
+                html += this.formatMetadataField(key, metadata[key]);
+            }
+        }
+
+        // Show generation info last if there's no other meaningful data
+        if (processedKeys.size <= 2 && metadata.generation) {
+            html += `<div class="metadata-section-title">Generation Info</div>`;
+            if (metadata.generation.generation_time) {
+                const genDate = new Date(metadata.generation.generation_time);
+                html += this.formatMetadataField('Generated', genDate.toLocaleString());
+            }
+        }
+
+        html += '</div>';
+        return html;
+    }
+
+    formatMetadataField(key, value) {
+        const displayKey = key.replace(/_/g, ' ').replace(/\b\w/g, l => l.toUpperCase());
+        
+        let formattedValue;
+        if (value === null || value === undefined) {
+            formattedValue = '<em>null</em>';
+        } else if (typeof value === 'object') {
+            if (Array.isArray(value)) {
+                if (value.length <= 3) {
+                    formattedValue = value.map(item => `<span class="metadata-tag">${item}</span>`).join(' ');
+                } else {
+                    formattedValue = `${value.slice(0, 3).map(item => `<span class="metadata-tag">${item}</span>`).join(' ')} <span class="metadata-more">+${value.length - 3} more</span>`;
+                }
+            } else {
+                // Show object as compact JSON for small objects, or just key count for large ones
+                const keys = Object.keys(value);
+                if (keys.length <= 3) {
+                    formattedValue = '<code>' + JSON.stringify(value) + '</code>';
+                } else {
+                    formattedValue = `<em>Object with ${keys.length} properties</em>`;
+                }
+            }
+        } else {
+            // Truncate long strings
+            const str = String(value);
+            formattedValue = str.length > 50 ? str.substring(0, 47) + '...' : str;
+        }
+
+        return `
+            <div class="metadata-field">
+                <span class="metadata-key">${displayKey}:</span>
+                <span class="metadata-value">${formattedValue}</span>
+            </div>
+        `;
+    }
+}
+
+// Global instance
+window.metadataPopup = new MetadataPopup();
+
+// Global function for template usage
+window.showMetadataPopup = function(button, plotName, metadata) {
+    window.metadataPopup.showPopup(button, plotName, metadata);
+};
diff --git a/templates/gallery.html b/templates/gallery.html
index 227b1d5..a0ee24c 100644
--- a/templates/gallery.html
+++ b/templates/gallery.html
@@ -41,6 +41,9 @@
         <a href="{{ item.pdf_href }}">
           <img src="{{ item.png_href }}" alt="{{ item.name }}">
         </a>
+        <button class="metadata-btn" onclick="event.stopPropagation(); showMetadataPopup(this, '{{ item.name|e }}', {{ item.metadata|default('{}')|tojson }})" title="View metadata">
+          ⋯
+        </button>
         <div class="plot-name" title="{{ item.name }}">{{ item.name }}</div>
       </div>
     {% endfor %}
@@ -183,6 +186,9 @@
     };
   </script>
 
+  <!-- Metadata Popup Script -->
+  <script src="{{ assets_path }}/js/metadata-popup.js"></script>
+
   <!-- Main JavaScript Application -->
   <script type="module" src="{{ assets_path }}/js/main.js"></script>
 </body>